Hoisington_Android_4e_PPT_CH01.pptx

Hoisington, Android Bootcamp for Developers Using Java, 4th Edition. © 2024 Cengage. All Rights Reserved. May not be scanned, copied or
duplicated, or posted to a publicly accessible website, in whole or in part. 1
1
Android Bootcamp
for Developers
Using Java, 4e
Chapter 1: Voilà! Meet the
Android
duplicated, or posted to a publicly accessible website, in whole or in part.

Icebreaker
• The class will be broken up into pairs of students.
• Each student will create three questions to ask their partner:
− One true/false question
− One question that can be answered with a number
− One question that requires a short answer
• Partners will take turns asking the questions they’ve prepared.
• Each student will then introduce their partner to the class using the information
they’ve learned.

Chapter Objectives (1 of 2)
When you complete this chapter, you will be able to:
• 01.01 Describe the market for Android applications
• 01.02 Identify the role of the Android platform in the mobile market
• 01.03 Describe the features of the Android phone
• 01.04 Identify the languages used in Android development
• 01.05 Describe the role of Google Play in the marketplace

• 01.06 Understand the connection between Windows and Android
• 01.07 Create an Android project using Android Studio
• 01.08 Design the user interface layout within the virtual device
• 01.09 Execute an Android application on an emulator
• 01.10 Open a saved Android project in Android Studio

1.1 Understanding the Market for Android
Applications
• Two primary mobile operating systems
− iOS for iPhone
− Google Android
• Recently, the Google Android phone has become the sales leader
• Apps: mobile applications created for smartphones

1.2 The Role of the Android in the Mobile
Market
• Open-Source Platform
− Android is an open-source operating system—no company or individual defines
the features or direction of the development
− Open Handset Alliance: an open-source business alliance of 80 firms that develop
standards for mobile devices
• Android Open-Source Devices
− Android smartphones, tablets, and smartwatches are sold by many companies
− As you develop an app, you test it using an emulator, which duplicates how the
app looks and feels on a particular device

1.3 Features of the Android Phone (1 of 3)
Feature Description
3D graphics The interface can support 3D graphics for a 3D interactive game experience or 3D
image rendering.
Split screen A split-screen, multiwindow feature displays more than one Android application at
the same time. Watch a movie on the left side and hold a video call with your
friends who are also watching the movie.
Dark mode The Dark mode feature helps to save the phone’s battery life. Blank white space
consumes more power and drains the battery.
Facial recognition Android provides this high-level feature for automatically identifying or verifying a
person’s face from a digital image or a video frame.
Front- and rear-facing
camera
Android phones can use either a front- or rear-facing camera, allowing developers
to create applications involving video calling.

Feature Description
Multiple language
voice-to-text support
Android supports multiple human languages. Android provides a feature of
converting text to speech in different languages. Text messages can be read aloud
to help people who are visually impaired.
On-screen keyboard The on-screen keyboard offers suggestions for spelling corrections as well as
options for completing words you start typing. The on-screen keyboard also
supports voice input.
Power management Android identifies programs running in the background that are using memory and
processor resources. You can close those apps to free up the phone’s processor
memory, extending the battery power.
Gaming For optimized gaming, Android supports the use of a gyroscope, gravity and
barometric sensors, linear acceleration, and rotation vectors, which provide game
developers with highly sensitive and responsive controls.

Feature Description
Voice-based
recognition
Android recognizes voice actions for calling, texting, and navigating with the phone.
Wi-Fi Internet tethering Android supports tethering, which allows a phone to be used as a wireless or wired
hotspot that other devices can use to connect to the Internet.

1.4 Languages Used in Android Development
(1 of 4)
• Java is an object-oriented programming language patterned after the C++
language
• Java and Kotlin can be used to code Android apps
• Android Studio
− An integrated development environment (IDE) for building and integrating
application development tools and open-source projects
− Includes the Android Software Development Kit (SDK)
− XML is used to assist in the layout of the Android emulator

(2 of 4)
Figure 1-4 Android Studio
running Java code

(3 of 4)
• Android Emulator
− Design, develop, prototype, and test Android apps without using a physical
device
− Mimics almost every feature of a real Android handset, except placing phone
calls
• Versions of Android
− First release was 1.0 (September 2008)
− Each subsequent release adds features and fixes known bugs

(4 of 4)
• Versions of Android (continued)
− Android has adopted a naming system based on treats/desserts
− When the revision level reached 10.0, Android started emphasizing revision
number over names
− Most recent versions were Android 12.0 (Snow Cone, October 2021) and
Android 13.0 (Tiramisu, October 2022)

Activity 1.1: Knowledge Check
(1 of 2)
1. What is the name of the organization that sets the standards for Android
mobile devices?
2. Name at least four types of devices that run the Android OS.

(2 of 2)
3. Should a developer target only the most recent version of the Android OS
when creating an app?
4. What is the name of the current version of the Android OS?

Activity 1.1: Knowledge Check Answers
(1 of 2)
1. What is the name of the organization that sets the standards for Android
mobile devices?
Answer: Open Handset Alliance
2. Name at least four types of devices that run the Android OS.
Answer: Smartphones, foldable phones, tablets, watches, MP4 players,
automobiles, and Internet TVs

(2 of 2)
3. Should a developer target only the most recent version of the Android OS
when creating an app?
Answer: No. To support as many Android devices as possible, you should set
the minimum development version to the lowest available that allows your app
to provide its core feature set.
4. What is the name of the current version of the Android OS?
Answer: Android 13.0 (internal name: Tiramisu)

1.5 Google Play in the Marketplace (1 of 2)
• The Android platform consists of the Android OS, application development tools,
and a marketplace
• Apps are compiled into package files with an .apk extension
• Google Play (http://play.google.com) sells and deploys all apps
• Programs must meet minimum standards, including:
− Reliability
− Efficiency
− Performance

1.5 Google Play in the Marketplace (2 of 2)
• Developers must sign an agreement and pay a one-time registration fee
(currently $25) to publish apps on Google Play
• Apps offered for free are free to publish
• For paid apps, standard split is 85% of sales for the developer and 15% for
wireless carriers for the first $1 million of annual earnings selling digital goods or
services
• Also sold through the Amazon Appstore
− Pays developers 80% of the sale price for sold apps and grants 10% of their
Appstore revenue as an Amazon Web Services credit

1.6 The Connection between Windows and
Android
• Beginning with Windows 11, you can download Android apps to your PC from
the Microsoft Store
• Android apps are also available for Windows-based tablets and other touch
devices
• Phone Link App
− The Microsoft Phone Link app allows you to connect an Android phone to a
Windows 11 PC
− Enables text messaging, notifications, and transfer of photos from the phone
on the PC

1.7 Creating an Android Project Using
Android Studio (1 of 8)
• Install Android Studio from developer.android.com/studio
• Opening Android Studio to Create a New Project
− Name: the human-readable title for your app
− Package name: the Java package namespace for the source code
− Save location on your hard drive or USB drive
− Minimum SDK: the minimum API level required by your app
− Language (Java or Kotlin)

• Creating the Hello Android World Project
− Android Studio facilitations app creation for various form factors
− Two most common projects: Empty Activity and Basic Project
− To create a new Android project, you open Studio, click the New Project
button, and make selections and entries for the project specs

Figure 1-8 Welcome to
Android Studio window

Figure 1-9 New Project
window with Empty Activity

Figure 1-10 Creating Empty
Activity

Figure 1-11 Android Studio
project view

• Building the User Interface
− The user interface must be intuitive
− The user interface must not distract from functionality
− Java code or XML layout files are needed
− The XML method is preferred because it allows you to design a user
interface without writing large amounts of code

• The Android Project View
− The Android project view contains the key source application folders for a
project: manifests, java, and res
− The manifests folder includes the AndroidManifest.xml file, which
contains all the information about the application that Android needs to run
− The java folder contains the Java code source files
− The res folder contains resources the app may need: images, music, video,
and the user interface named activity_main.xml

1.8 The User Interface Layout within the
Virtual Device (1 of 12)
• The Android SDK includes layout files called activity_main.xml in the res/layout
folder of the app
• The Layout Editor contains the Palette, Component Tree, toolbar, Design
editor, and Attributes pane
• Layout: a container that holds as many widgets as needed
• Widget: a single element (a.k.a. object), such as a Button from the Palette

Figure 1-12 Coding window in
Android Studio

• The Attributes pane contains the attributes and settings of the currently active
app project or object
• Attribute: a characteristic of an object that describes what that object can do
• Android Studio displays an emulator configuration called the Android Virtual
Device (AVD) for design and layout purposes
• To change the virtual device, you open the activity_main.xml file to open the
Layout Editor, then click the Device for Preview (D) button and select the
desired device

Figure 1-13 Layout Editor for
emulator layout design

Figure 1-14 Device for
Preview button

Figure 1-15 Generic phone
selected for Device for
Preview

• When you select the default TextView component, its text is displayed in the
Component Tree
− The Component Tree displays widgets in the order they were placed on the
emulator
• Within the Common Attributes section of the Attributes pane, you can see the
text attribute of the component, which is the text it contains

Figure 1-16 Design editor

Figure 1-17 Attributes pane

• The TextView Component
− Text can be updated by:
 Changing the hard-coded value for the text attribute in the Attributes
pane
 Modifying resource files
 Changing the application XML source code
− It is good programming practice to add an id attribute to each component
(object) for use in Java code

Figure 1-18 Emulator with
TextView control and text
attribute

Figure 1-19 The id attribute

1.9 Executing an Android Application on an
Emulator (1 of 2)
• The Android emulator (virtual device) runs slowly
− Even when idling, it consumes significant CPU time
• To run and automatically save your app, click the Run button
• Click the Terminate button to stop the emulator from running

1.9 Executing an Android Application on an
Emulator (2 of 2)
Figure 1-20 Hello Android
World app displayed in
emulator

1. In Android Studio, objects such as buttons and text boxes are called _____.
2. Java code source files are stored in the _____ folder.
3. Testing the app is done in a(n) _____.

1. In Android Studio, objects such as buttons and text boxes are called _____.
Answer: widgets
2. Java code source files are stored in the _____ folder.
Answer: java
3. Testing the app is done in a(n) _____.
Answer: emulator

1.10 Opening a Saved Android Project in
Android Studio
• To load a saved project, open Studio and then choose the project to open
− Click on it in the Recent Projects column or
− Click Open an existing Android Project in the Quick Start column, navigate to
it, and click the OK button

Self-Assessment
1. After reading about the market and requirements for software development for
Android devices, what skills would you like to gain or improve before you
begin developing Android apps for publication? What aspects of the market for
these apps would you like to learn more about?
2. What is your initial impression of the Android Studio and Android SDK tools
available to you as an Android developer?

Summary
• Click the link to review the objectives for this presentation.
Chapter objectives

48
Android Bootcamp
for Developers
Using Java, 4e
Chapter 2: Simplify! The Android
User Interface

• 02.01 Develop a user interface using the TextView, ImageView, and Button
components
• 02.02 Add text using the String table in the Translations Editor
• 02.03 Construct the user interface using a ConstraintLayout
• 02.04 Plan out program design
• 02.05 Create multiple Android activities

• 02.06 View activities in the Android Manifest file
• 02.07 Write code using the onCreate( ) method
• 02.08 Create a Button event handler
• 02.09 Code a Button event handler
• 02.10 Correct errors in code
• 02.11 Run the completed app in the emulator

2.1 Designing an Android App (1 of 5)
Figure 2-1 Easy Recipes
Android app (left)
Figure 2-2 Second screen with
recipe (right)

• Designing apps is like constructing a building
• The Big Picture: To create the Easy Recipes app, you follow a set of steps that
you repeat every time you create an Android application
− Create the user interface (XML layout) for every screen
− Create a Java class (Activity) for every screen
− Code each Java class with appropriate objects and actions
− Test the application in the Android phone emulator

• Using the Android User Interface
− Interface: the space where interactions occur between people and the app
− Android apps run on various form factors
− The layout is stored as XML code
 Special Android-formatted XML code is extremely compact
 XML is a set of instructions for placing components on the screen

Figure 2-4 Creating an empty
activity for the Easy Recipes
app

Figure 2-5 Android
Studio open and
ready for you to
design the Easy
Recipes app

2.2 Using the String Table in the Translations
Editor (1 of 5)
• The Translations Editor in Android Studio can display the original text in the
language in which it was programmed, or the language of the current locale plus
culturally specific settings
• The String Table
− Android provides the strings.xml file or String table inside the Resources
folder
− strings.xml: a default file that is part of every Android application and
contains commonly used strings for an application
− string: a series of alphanumeric characters that can include spaces

Editor (2 of 5)
• The String Table (continued)
− Localization: the use of the String table to change text based on the user’s
preferred language
− Every string is composed of a key (a.k.a. id attribute), which is the name of
a component, and a default value, which is the text associated with the
component
− To create an application that is accessible to those with visual disabilities,
add descriptions to the user interface components that can be read out
loud to your user by a speech-based accessibility service such as a screen
reader

Editor (3 of 5)
Figure 2-7 The strings.xml tab
displaying XML code

Editor (4 of 5)
Figure 2-10 Adding another
string to the String table

Editor (5 of 5)
Figure 2-11 Completed String
table on the Translations
Editor tab

2.3 Constructing the User Interface with the
ConstraintLayout (1 of 18)
• The Android user interface includes a layout resource designer called the
ConstraintLayout in the Component Tree
− Organizes how components appear on the app’s screens
− Provides more flexibility in positioning components than other layouts
− Constraints: the building blocks in an Android layout that attach or align a
component to the screen, either by attaching it vertically and horizontally to
the edges of the screen or aligning it with another component (or parent) on
the screen
− Constraints are used to create a Responsive Design UI

• Constraint Handles
− Four circular dots on the edges of a selected component
− A Constraint component must have at least two constraints—a vertical and a
horizontal one
− If you drag all four Constraint handles to the four edges of the emulator
screen, you can then drag the component anywhere on the screen and it will
stay in that location when you run the app
− In the ConstraintLayout, a nonconstrained component will float to the top of
the screen when the app is run

• Constraint Handles (continued)
− A white Constraint handle means
that the component is not aligned
− A blue Constraint handle means
that the component is aligned with
the screen or another component
− Corner boxes resize the
component
Figure 2-12 The four circles
are Constraint handles

• XML Code
− After you move the Constraint handles in the Design view, Android Studio
updates your layout resources as XML code in the res/layout resource
directory
− Other common layouts used in Android Studio include:
 LinearLayout
 RelativeLayout
 TableLayout
 GridView

Figure 2-13 ConstraintLayout
XML code

• The Easy Recipes Opening User Interface: To change a component's attributes,
select it and use the Attributes pane
• Android Text Attributes
− The text attribute uses text from a string resource to display within the
component
− The textSize attribute can use various units of measurement
 The preferred unit is often sp (scaled-independent pixels)
 Other units: inches (in), millimeters (mm), pixels (px), density-
independent pixels (dp or dip)

Figure 2-16 The text attribute
with @string used to display
the String table

Figure 2-17 TextView text
displayed in emulator after
@string selected

Figure 2-18 Updating the
textSize of the TextView
component

• Adding a File to the Resources Folder
− Graphics used in ImageView components must first be placed in the
res/drawable folder
− Android supports .png (preferred), .jpg (acceptable), and .gif (discouraged)
graphic formats
− Android categorizes device screens based on size and density
− Android creates a Drawable resource for images when you save them in the
res/drawable folder

Figure 2-19 The sorbet.png
file copied into the drawable
folder within the res folder

• The ImageView Component
− An ImageView component can display an icon, a company logo, or a
graphic on the Android screen
− Reminder: The image to be used should be placed in a drawable resources
folder before the ImageView component is placed in the emulator

Figure 2-23 ImageView
component with image
displayed in the emulator and
the id entered

Figure 2-24 The
contentDescription set for
accessibility

• Adding a Button Component
− Button components are commonly used in GUIs
− The Android SDK includes four types of button components: Button,
FloatingActionButton, ToggleButton, and ImageButton
− backgrountTint: an attribute that can be added to a component to set a
background color
− textColor: an attribute that sets the color of the text in a component

Figure 2-26 Button
component placed on
emulator and the id named

Figure 2-27 Button displaying
larger text

Figure 2-28 Button with
colors displayed for
background tint color

Activity 2.1: Knowledge Check (1 of 2)
1. List the major steps you follow to create an Android application.
2. Android loads text resources from the project's _____.
3. Which Android layout provides flexibility in positioning components and
facilitates making your layout a Responsive Design UI?

4. Which unit of measurement is often preferred for the textSize attribute? Why?
5. To display an illustration or photo in an Android app you use a(n) _____.

(1 of 2)
1. List the major steps you follow to create an Android application.
Answer: (1) Create the user interface (XML layout) for each screen.
(2) Create a Java class (Activity) for every screen.
(3) Code each Java class with the appropriate objects and actions.
(4) Test the application in the emulator.
2. Android loads text resources from the project's _____.
Answer: string table or strings.xml file
3. Which Android layout provides flexibility in positioning components and
facilitates making your layout a Responsive Design UI?
Answer: ConstraintLayout

(2 of 2)
4. Which unit of measurement is often preferred for the textSize attribute? Why?
Answer: sp (scaled-independent pixels), because it will scale the font to meet
the user's size preference
5. To display an illustration or photo in an Android app you use a(n) _____.
Answer: ImageView component

2.4 Planning Out Program Design
• Phases in the program development life cycle:
− Gather and analyze the program requirements
− Design the user interface
− Design the program processing objects
− Code the program
− Test the program
• Creating Activities
− Activity: a screen, constructed from XML files and a Java class

2.5 Creating Multiple Android Activities
(1 of 2)
• A class describes a group of objects and serves as a blueprint, or template, for
creating those objects
• An object is a specific, concrete instance of a class
• When you create an object, you instantiate it, meaning you define one
particular variation of the object within a class
• Each screen represents one Activity, and each Activity must have a matching
Java class file within the java folder
• The convention is to use Pascal case for Java class names

2.5 Creating Multiple Android Activities
(2 of 2)
Figure 2-34 New Recipe class
in the Easy Recipes project

2.6 Viewing Activities in the Android Manifest
File (1 of 3)
• The Android Manifest file (AndroidManifest.xml) contains:
− The name of the Java application
− A listing of each activity
− Permissions needed to access other Android functions (such as the Internet,
services, and broadcast receivers)
− The minimum level of the Android API
• Android Studio automatically adds each activity you create to the Android
Manifest file

File (2 of 3)
Figure 2-35
AndroidManifest.xml

File (3 of 3)
• Coding the Android Activity
− The entry point of the Activity class is the onCreate() event handler method
 Where you initialize the Activity by placing it on the top of Android's stack
of Activities
− Method: a set of Java statements that can be included inside a Java class; a
piece of code that performs some type of action
− Method body: a collection of statements that defines what the method does

2.7 Writing Code Using the onCreate()
Method (1 of 2)
• Syntax for the onCreate() method:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
• This method has a void return type, which means it does not return anything
• The Java code necessary to display the content of a specific screen is called
SetContentView, which has the following syntax:
setContentView(R.layout.activity_main);

2.7 Writing Code Using the onCreate()
Method (2 of 2)
Figure 2-36 MainActivity.java
code for onCreate( ) method

2.8 Creating a Button Event Handler
(1 of 3)
• Event handler: a part of a program coded to respond to a specific event
• Tapping a button is called a click event in Java code
• Java code for an event handler must contain the following sections:
− A class attribute to hold a reference to the Button object:
Button = (Button)findViewById(R.id.btRecipe);
 Includes the findViewById() method to find a layout XML file
− An OnClickListener() method to await the button click action's onClick()
method to respond to the click event

(2 of 3)
• When you import the Button type as an Android widget, the button package
becomes available throughout the app
− An import statement makes more Java functions available to your app
• After the Button attribute is referenced in MainActivity.java, an OnClickListener()
method is necessary to detect when the user taps an on-screen button
• When an OnClickListener is placed in the code window, Java creates an onClick
auto-generated stub—a piece of code that serves as a placeholder to declare
itself

(3 of 3)
• Syntax for an OnClickListener() method that listens for a Button:
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
}
});
• The startActivity() method creates an intent to start another Activity
− Two parameters: context and name of Activity to open
− Syntax: startActivity(new Intent(MainActivity.this,
Recipe.class));

2.9 Coding a Button Event Handler
(1 of 3)
Figure 2-38 Button
instantiated with Button
library added

(2 of 3)
Figure 2-40 The
setOnClickListener added
with auto-complete feature

(3 of 3)
Figure 2-41 Complete code
for MainActivity.java—
startActivity will launch the
second screen’s Recipe.class
when the user clicks the
button

1. Name the phases of the development life cycle in order.
2. The file included in each Android application that provides essential
information such as the minimum API level to the Android device is called
_____.

3. Which Java method initializes an Android Activity?
4. A part of a program that responds to a user interaction such as tapping an on-
screen button is called a(n) _____.
5. Which Java method is necessary to detect a user interaction with the app?

(1 of 2)
1. Name the phases of the development life cycle in order.
Answer:
(1) Gather and analyze the program requirements.
(2) Design the user interface.
(3) Design the program processing objects.
(4) Code the program.
(5) Test the program.
2. The file included in each Android application that provides essential
information such as the minimum API level to the Android device is called
_____.
Answer: the Android Manifest or AndroidManifest.xml

(2 of 2)
3. Which Java method initializes an Android Activity?
Answer: onCreate()
4. A part of a program that responds to a user interaction such as tapping an on-
screen button is called a(n) _____.
Answer: event handler
5. Which Java method is necessary to detect a user interaction with the app?
Answer: OnClickListener()

2.10 Correcting Errors in Code
Figure 2-42 Syntax error

2.11 Saving and Running the Application
• Each time an Android application is tested in the emulator, the programming
design and code are automatically saved
• Click the toolbar's Save All button to save the project
• Click the toolbar’s Run app button to test the application in the emulator
− The first time an app is executed, you will be prompted to choose an
emulator

Self-Assessment
1. What is your opinion of the Android Studio user interface design tools? Are
there any improvements you'd like to see? Which tools do you anticipate using
most often when creating or updating Android apps?
2. When creating the app project for Chapter 2, which did you enjoy more:
working with the XML layout tools in Studio or writing Java code? How do you
expect to use these UI creation skills in your future career?

Summary
Chapter objectives

105
Android Bootcamp
for Developers
Using Java, 4e
Chapter 3: Engage! Android
User Input, Variables, and
Operations

• 03.01 Collect user input
• 03.02 Add a Text Number component
• 03.03 Add a string array
• 03.04 Change the background attribute
• 03.05 Set the hint attribute for a Text component
• 03.06 Develop a user interface using a Spinner component

• 3.07 Add a prompt and entries to a Spinner component
• 3.08 Code the EditText class for the Text Number component
• 3.09 Code the Spinner component
• 3.10 Instantiate the Button component and variables
• 3.11 Code the getText() method

• 3.12 Understand arithmetic operations
• 3.13 Code the setText( ) method

3.1 Collecting User Input (1 of 4)
Figure 3-1 Opening screen for
Concert Tickets app

• Processes required to create this application:
− Define display text using the Translations Editor and strings.xml file
− Set the background color
− Define a Text Number component
− Define a Spinner component
− Convert string data to numeric data
− Perform arithmetic operations with user-entered data
− Display the results, properly formatted, to the user

• Simplifying User Input
− The onscreen keyboard is called a soft keyboard
− Input can come in the form of tapping or gestures (using two fingers to pan,
rotate, or zoom)
− The primary design challenge is to simplify the user experience
 Use legible fonts, simplify input, and optimize each device’s capabilities
to maximize user experience

• Using Android Text Components
− Text entered via a soft or physical keyboard is the most common type of
mobile input
− Text components can request different input types (e.g., plain text, phone
number, various types of numeric values)
− The component type can constrain the characters available
• User Experience
− User experience refers to all aspects of interaction with a device

3.2 Adding a Text Number Component
(1 of 3)
• You can use the id attribute in the Attributes pane to enter a name that begins
with the prefix tv (for TextView)
− Use descriptive names like tvTickets
• Using the String Table
− String items displayed in the components of an app can be stored in the
string table (strings.xml)
− A string array can be used to store a group of related strings

(2 of 3)
Figure 3-5 Adding strings in
the Translations Editor

(3 of 3)
Figure 3-6 String table

3.3 Adding a String Array (1 of 2)
• A string array defines a string resource of related items in a central location
within strings.xml
• An item defines an individual entry within a string array
• As you type the string array XML code, the Android Studio editor offers
suggestions in a panel that can complete a statement

3.3 Adding a String Array (2 of 2)
Figure 3-9 The string array
named tvGroup with three
items added in XML code

3.4 Changing Background Attributes
(1 of 4)
• The Android background feature can help provide an app's individual flair
• The background is white by default
• To change it, set the background attribute in the Attributes pane

(2 of 4)
Figure 3-10 Changing the
background color

(3 of 4)
Figure 3-11 Title added to
emulator

(4 of 4)
Figure 3-12 Adding a Text
Number component

3.5 Setting the Hint Attribute for a Text
Component (1 of 2)
• A hint is a short description of a component that is visible as gray text (also
called a watermark) inside a Text Number component or any Text input
− Often used to provide guidelines about the input expected in a component
for the user
• You can change the color of the hint by changing the textColorHint attribute
− May be necessary to ensure adequate contrast between the text and
background

3.5 Setting the Hint Attribute for a Text
Component (2 of 2)
Figure 3-15 Warning symbol
removed from Text Number
component

1. If a component holds multiple text strings, it is best to store them in a(n)
_____.
2. To change the screen color for an activity in your app, you set the _____.
3. When you see gray text describing what sort of data to enter within a text entry
box in an app, you are looking at a(n) _____.

1. If a component holds multiple text strings, it is best to store them in a(n)
_____.
Answer: string array
2. To change the screen color for an activity in your app, you set the _____.
Answer: background attribute
3. When you see gray text describing what sort of data to enter within a text entry
box in an app, you are looking at a(n) _____.
Answer: hint

3.6 Developing a User Interface Using a
Spinner Component
• A Spinner component is similar to a
drop-down list for selecting a single
item from a fixed list
• The Spinner component displays a
prompt with a list of strings called
items
• Figure 3-16 Spinner dialog box
displaying the three concert groups

3.7 Adding a Prompt and Entries to a Spinner
Component (1 of 6)
• A prompt, which can be used to display instructions at the top of the Spinner
control, is stored in strings.xml and is named prompt
• Using Entries
− The Spinner attribute called entries connects the string array in strings.xml
to the Spinner component so the entries can be displayed in the application
− The spinnerMode attribute sets the component to dialog mode or drop-
down mode
− The layout_width and layout_height attributes set the dimensions

Component (2 of 6)
Figure 3-18 Pick a Resource
dialog box with tvGroup
string array selected

Component (3 of 6)
• Adding the Button, TextView, and ImageView Controls
− ImageView components should have a content description for visually
impaired users
− This description is provided by setting the contentDescription attribute

Component (4 of 6)
Figure 3-20 Adding a Button
component

Component (5 of 6)
Figure 3-21 Adding a
TextView component

Component (6 of 6)
Figure 3-22 Adding an
ImageView component with a
contentDescription attribute

3.8 Coding the EditText Class for the Text
Number Component (1 of 2)
• A Java variable is used to contain data that changes during the execution of a
program
• A final variable can be initialized only once
− Attempting to reassign the value results in a compile error when the
application runs
• For the concert tickets app, you insert code to create the tickets variable
containing the extracted EditText class text:
final EditText tickets =
(EditText)findViewById(R.id.tvTickets);

3.8 Coding the EditText Class for the Text
Number Component (2 of 2)
Figure 3-23 EditText code for
Text Number component

3.9 Coding the Spinner Control
Figure 3-24 Spinner
component code

3.10 Instantiating the Button Component and
Variables (1 of 6)
• An OnClickListener waits in the background and listens for the user to click a
button
• Clicking the button activates a Button event, triggering the Button event OnClick
handler to execute the associated code
• Code to instantiate the TextView component to a variable named result is used
to display the result of the ticket price calculation in the concert tickets app:
final TextView result =
((TextView)findViewById(R.id.tvResult));

Variables (2 of 6)
Figure 3-27 TextView
component code for the
result

Variables (3 of 6)
• Declaring Variables
− Two steps are necessary in order to use a variable: (1) declare the variable
and (2) assign a value to the variable
− The declared type of a variable determines which operations are allowed
− Java has eight built-in primitive (simple) types of data
• Primitive Data Types
− Java requires all variables to have a data type

Variables (4 of 6)
Type Meaning Range Default Value
byte Often used with arrays –128 to 127 0
short Often used with arrays –32,768 to 32,767 0
int Most commonly used number value –2,147,483,648 to 2,147,483,647 0
long Used for numbers that exceed int –9,223,372,036,854,775,808 to
9,223,372,036,854,775,807
0
float A 32-bit floating-point number +/–3.40282347 ^38 0
double Most common for decimal values +/–1.79769313486231570 ^308 0
char Used for single characters Characters 0
boolean Used for conditional statements True or false False

Variables (5 of 6)
• Primitive Data Types (continued)
− Sample variable initialization and declarations:
double costPerTicket = 89.99;
int numberOfTickets;
double totalCost;
String groupChoice;
• The String Data Type
− The String type is a class and not a primitive data type
− A string can be a character, word, or phrase

Variables (6 of 6)
• The String Data Type (continued)
− Most strings used in Java are objects of type String (e.g.,
String groupChoice;)
• Declaring the Variables in the Project
− Typically declared at the beginning of an activity
− Variables must be declared before you can use them

3.11 Coding the getText() Method
(1 of 2)
• Data stored in the EditText component can be read with the getText() method
• Data is read in as a string, by default
• A Parse class is used to convert strings into numbers
− Parse types include Integer.parseInt(), Float.parseFloat(),
Double.parseDouble(), and Long.parseLong()
• Sample code to extract a string and convert it into an integer:
numberOfTickets =
Integer.parseInt(tickets.getText().toString());

3.11 Coding the getText() Method
(2 of 2)
• Working with Mathematical Operations
− The ability to perform arithmetic operations is fundamental to many
applications
− Most programs require arithmetic operations to add, subtract, multiply, and
divide numeric data

1. A drop-down list for an Android app is created using a(n) _____.
2. The attribute that connects the choices for a drop-down list to their component
is called _____.
3. Which Java keyword prevents a variable from being reassigned?
4. Which Java method reads text stored in an EditText component?

1. A drop-down list for an Android app is created using a(n) _____.
Answer: Spinner component
2. The attribute that connects the choices for a drop-down list to their component
is called _____.
Answer: entries
3. Which Java keyword prevents a variable from being reassigned?
Answer: final
4. Which Java method reads text stored in an EditText component?
Answer: getText()

3.12 Understanding Arithmetic Operators
(1 of 3)
• Java's arithmetic operators are + (addition), – (subtraction), * (multiplication), /
(division), % (remainder), ++ (increment 1), and -- (decrement 1)
• The order of operations determines the sequence for performing calculations
when multiple operators are included in an expression
− Parentheses; ++ & --; *, /, & %; + & – (left to right)
• Formatting Numbers
− Java includes a class called DecimalFormat that provides patterns for
formatting numbers for output on the Android device

(2 of 3)
Figure 3-30 Calculating and
formatting the ticket cost

(3 of 3)
• Displaying Android Output: Computed results must be displayed
• Using the getSelectedItem() Method
− The getSelectedItem() method returns the text label of the currently
selected Spinner item
− Sample code that assigns a selected item to a String variable named
groupChoice:
groupChoice = group.getSelectedItem( ).toString( );

3.13 Coding the setText() Method
• The setText() method displays text in a TextView component
• You can concatenate text and string variable values using +, e.g.,
String mobile = "Android";
String completeSentence = mobile + " is a platform.";
• Sample statement using the setText() method to display text in a TextView
component named result:
result.setText("Cost for " + groupChoice + " is " +
currency.format(totalCost));

Self-Assessment
1. At this point, how comfortable are you using Java classes such as String and
Parse to accomplish the goals of a program? What else would you like to learn
about these Java classes?
2. Consider the Java methods used to code the sample concert ticket
application. How do you anticipate using these methods for your own app
development? What would their most common use cases be for you?

Summary
Chapter objectives

152
Android Bootcamp
for Developers
Using Java, 4e
Chapter 4: Explore! Icons and
Decision-Making Components

• 04.01 Create an Android project with a custom icon
• 04.02 Display the Action bar icon using code
• 04.03 Place a RadioGroup and RadioButtons in Android applications
• 04.04 Determine layouts with the layout:margin attributes
• 04.05 Align components using the foregroundGravity attributes

• 04.06 Add a RadioButton Group
• 04.07 Write code for a RadioButton component
• 04.08 Make decisions with conditional statements
• 04.09 Make decisions using an If statement
• 04.10 Make decisions using an If Else statement

• 04.11 Make decisions using logical operators
• 04.12 Display an Android toast notification
• 04.13 Use the isChecked() method with RadioButtons
• 04.14 Make decisions using nested If statements

4.1 Creating an Android Project with a
Custom Icon (1 of 12)
• We will be creating an app to convert pounds to kilograms and kilograms to
pounds
• App is designed to be used in a hospital setting to administer medication to
patients based on patient weight
• Hospital scales register pounds, whereas medication dosages are based on
patient weight in kilograms
• Formulas needed:
− Kilograms = pounds * 2.2
− Pounds = kilograms / 2.2

Figure 4-1 Opening screen of
the Medical Calculator
Figure 4-2 Results screen of
the Medical Calculator

• Steps to complete the app:
− Create a customized launcher icon
− Use code to add the icon for display in the Action bar
− Define a TextField for the data entry of the weight of the patient
− Define a RadioGroup to select a conversion of pounds to kilograms or
kilograms to pounds
− Display a toast message for data validation
− Convert data so it can be used for arithmetic operations

• Steps to complete the app (continued):
− Perform arithmetic operations on data the user enters
− Display formatted results

• Using the Launcher Icon
− The launcher icon opens the app from the home screen and represents the
app when it is published to Google Play
− A high-quality launcher icon can influence users to purchase your app
− Icons can establish brand identity
− Simple images with clear visual cues have a memorable impact
− Vector-based graphics are best for icon design because these images can
be easily scaled without loss of detail

• Using the Launcher Icon (continued)
− Google Play specifies the size and format of all launcher icons
− Should be saved with the .png file format/extension
− When you publish an app to Google Play, you must provide a 512 × 512-
pixel, high-resolution application icon in the developer console as you upload
your program
 This icon is displayed on the Google Play site to provide a description of
the app and does not replace your launcher icon
− Google Play's naming convention for launcher icons: ic_launcher

Resolution Dots Per Inch (dpi) Size (px)
ldpi (low-density screen) 120 36 × 36
mdpi (medium-density screen) 160 48 × 48
hdpi (high-density screen) 240 72 × 72
xhdpi (extra high-density screen) 320 96 × 96
xxhdpi (extra extra high-density screen) 480 144 × 144
xxxhdpi (extra extra extra high-density screen) 640 192 × 192

• Customizing a Launcher Icon
− Image Asset Studio: Android Studio tool that helps you generate your own
app icons from images
 Generates a set of icons at the appropriate resolution for each pixel
density your app supports
− Use the built-in Image Asset Studio wizard to create these multiple icons and
store them in the correct folders

Figure 4-6 Default launcher
icons in the Asset Studio

Figure 4-7 Custom launcher
icons

Figure 4-8 Confirmed icon
path in Asset Studio displayed
in res/mipmap folders

Figure 4-9 Resized custom
icons and their pathways in
the mipmap folder

4.2 Displaying the Action Bar Icon Using
Code (1 of 4)
• An Action bar icon is considered a logo that represents what the program’s
function is in a single glance
− For example, the medical symbol conveys the purpose and identity of the
app
• Supporting code needed in MainActivity.java to display the image in the Action
bar:
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setLogo(R.mipmap.ic_launcher);
getSupportActionBar().setDisplayUseLogoEnabled(true);

Code (2 of 4)
Figure 4-11 Icon displayed in
running app in the emulator

Code (3 of 4)
• String Table
− String resources are stored within the /res/values/strings.xml file
− Any strings you add to the strings.xml file are accessible within your
application

Code (4 of 4)
Figure 4-12 Translations
Editor with new strings in the
String table

4.3 Placing a RadioGroup and RadioButtons
in Android Applications (1 of 2)
• RadioButton components are used to select or deselect an option
− Can be arranged horizontally or vertically
− Have a label defined by the Text attribute
− Checked attribute can be set to true or false
− Typically used together in a RadioGroup container
 Only one RadioButton in the group can be selected at a time
− It saves time to offer a default selection (checked = true) for the option that is
used most often
172

4.3 Placing a RadioGroup and RadioButtons
in Android Applications (2 of 2)
• Changing the Text Color of RadioButton and CheckBox Components
− Hexadecimal color code: a triplet of three colors
 Example: #FF0000 is a true red
 Color system used by the Android platform
− Codes range from 00 to FF (00 = none, FF = full)
− Codes are identified by a pound sign, followed by the red, green, and blue
values contained in the color
173

4.4 Determining Layouts with the
layout:margin Attributes
• You can change a component's alignment after placing it on the UI by adjusting
its Gravity settings
• The layout:margin attribute allows for more flexibility in controlling your layout
− You can change all margins equally or change the left, top, right, and bottom
margins individually
• Set density-independent pixel (dp) values instead of “eyeballing” to create equal
spaces around components
• Using the same specified margins creates a symmetrical layout

(1 of 2)
1. What is an app's opening icon called?
2. What tool can you use to generate a launcher icon from an image?
3. RadioButton components are typically used together in a(n) _____.
4. What is #FF0000?

(2 of 2)
5. What settings are used to change the alignment of an object?
6. Which attribute can you use to set the spacing around each side of an object
individually?

(1 of 2)
1. What is an app's opening icon called?
Answer: The launcher icon
2. What tool can you use to generate a launcher icon from an image?
Answer: Image Asset Studio
3. RadioButton components are typically used together in a(n) _____.
Answer: RadioGroup
4. What is #FF0000?
Answer: The hexadecimal color code for a true red color

(2 of 2)
5. What settings are used to change the alignment of an object?
Answer: Gravity settings
6. Which attribute can you use to set the spacing around each side of an object
individually?
Answer: layout:margin attribute

4.5 Aligning Components Using the
foregroundGravity Attributes
• A component's gravity can be changed using the Attributes pane or with a
toolbar shortcut
• The foregroundGravity tool changes the linear alignment of a component
• Layout gravity is similar to the alignment feature in Microsoft Office that allows a
component to snap to the left, center, right, top, or bottom

4.6 Adding the RadioButton Group and Other
Components (1 of 5)
• When naming a RadioButton with the id attribute, use a name that begins with
the prefix rb, which represents a radio button in the code
• Completing the User Interface
− Remember to create a clean layout and use the entire screen effectively

Components (2 of 5)
Figure 4-15 Text Number
component and
foregroundGravity attribute
to center hint text

Components (3 of 5)
Figure 4-16 RadioGroup
component

Components (4 of 5)
Figure 4-17 Two RadioButton
components with first
RadioButton checked

Components (5 of 5)
Figure 4-20 TextView
component to display results

4.7 Coding a RadioButton Component
(1 of 3)
• Java syntax to reference each of the RadioButton components using the
findViewById() method:
final RadioButton lbToKilo = (RadioButton)
findViewById(R.id.rbLbToKilo);
final RadioButton kiloToLb = (RadioButton)
findViewById(R.id.rbKiloToLb);
• Coding the Button Component
− The Button component detects user interaction using an event listener

(2 of 3)
Figure 4-22 EditText and
RadioButtons referenced

(3 of 3)
Figure 4-24 OnClickListener
for the Button component

4.8 Making Decisions with Conditional
Statements
• Decision structure: a fundamental computer programming structure that tests
a condition and then follows a path specified for the result
• A conditional statement tests a condition and returns a result of either true or
false
− Boolean operators have two values, which are either true (1) or false (0)
− When you compare values, Java returns a Boolean value of true or false

4.9 Making Decisions Using an If Statement
• An If statement tests a condition and executes the statement(s) between its
curly braces only when the condition is true
• Syntax for simplest form of the Java If statement:
if (condition) {
//Statements completed if true
}
• If the condition is false, program execution continues with the statements after
the closing brace

4.10 Making Decisions Using an If Else
Statement (1 of 3)
• An If Else statement executes one set of instructions if a condition is true and
another set of instructions if the condition is false
• Java syntax for the If Else statement:
if (condition) {
//Statements completed if condition is true
} else {
//Statements completed if condition is false
}

Statement (2 of 3)
Relational Operator Meaning Example Resulting Condition
== Equal to 6 == 6 True
!= Not equal to 4 != 7 False
> Greater than 3 > 2 True
< Less than 8 < 1 False
>= Greater than or equal to 5 >= 5 True
<= Less than or equal to 9 <= 6 False

Statement (3 of 3)
• Relational Operators
− Relational operators are used in conditional statements to express the
relationship between the numbers being tested
− Java strings are compared using the equals() method
− The compareTo() method is used to determine the alphabetical order of
strings
 Returns a negative integer if the first string precedes the second
 Returns 0 if they are equal
 Returns a positive integer if the first string follows the second

4.11 Making Decisions Using Logical
Operators
• When more than one condition is included in an If statement, the conditions are
called a compound condition
• Java logical operators are needed to control the flow of execution with
compound conditions
− && means and—all Boolean conditions must be true
− || means or—at least one Boolean condition must be true
− ! means not—it reverses the meaning of a Boolean condition
• Data validation: the practice of checking the integrity, accuracy, and structure of
a program before it is used for a business operation

4.12 Displaying an Android Toast Notification
• A toast notification communicates messages to the user unobtrusively
− Message slides upward into view like toast popping out of a toaster
• The toast notification code uses a Toast object and the makeText() method with
three parameters: context (activity name), message text, and duration of display
• Java syntax: Toast toast = Toast.makeText(context, text,
duration).show();
− Duration is LENGTH_SHORT or LENGTH_LONG
− The show() method displays the Toast object

4.13 Using the isChecked() Method with
RadioButton Components
• The isChecked() method determines if a RadioButton (or CheckBox) object
has been selected
• Example syntax:
if (lbToKilo.isChecked) {
//Statements completed if condition is true (Boolean
value)
} else {
//Statements completed if condition is false (Boolean
value)
}

1. What kind of statement is used to test a radio button's state?
2. What Java method is used to determine whether or not a radio button has been
selected?
3. When you use a(n) _____ statement in a decision structure, code is executed for
either a true or a false result.
4. What do we use to compare strings to see if they are equal?
5. What are the three common logical operators?

1. What kind of statement is used to test a radio button's state?
Answer: A conditional statement
2. What Java method is used to determine whether or not a radio button has been
selected?
Answer: isChecked()
3. When you use a(n) _____ statement in a decision structure, code is executed for
either a true or a false result.
Answer: If Else
4. What do we use to compare strings to see if they are equal?
Answer: Java equals() method
5. What are the three common logical operators?
Answer: && (And), || (Or), ! and (Not)

4.14 Using Nested If Statements (1 of 5)
• When you place an If statement within another If statement, the inner If
statement is said to be nested within the outer If statement
• Coding the Button Event
− The syntax Double.parseDouble converts input to a Double data type
− Integer.parseInt converts input to an Integer data type
− The DecimalFormat object is used to format data for display

Figure 4-26 DecimalFormat
code used to round to the
nearest tenth

• Coding the Nested If Statements
− In the Medical Calculator app, nested If statements are used
 Outer If statements determine the conversion option selected
 Inner If Else statements display the result only if the weight is within 500
pounds or 225 kilograms (the If branch)
 If the weight is out of this range, a toast notification is displayed instead
(this is the Else branch)

Figure 4-31 Completed code
for If Else statements

Figure 4-32 Running app and
toast notification

Self-Assessment
1. How much attention do you pay to the launcher icons for apps that you use?
Do you think that launcher icons have impacted your choices regarding which
apps to download?
2. What previous experience do you have designing and coding decision
structures? Would you have coded the logic for the Medical Calculator app
differently? If so, explain why.
3. Describe how you expect to use toast notifications in apps that you develop.

Summary
Chapter objectives

205
Android Bootcamp
for Developers
Using Java, 4e
Chapter 5: Investigate! Android
Lists, Arrays, Switch Statements,
and Web Browsers

• 05.01 Create an Android project using a list
• 05.02 Add a ListView layout with XML code
• 05.03 Create an array
• 05.04 Initialize a ListView layout component
• 05.05 Display an array in the ListView with an ArrayAdapter

• 05.06 Call the setOnItemClick() method
• 05.07 Create a decision structure using a Switch statement
• 05.08 Describe the purpose of intents in Android
• 05.09 Launch a browser from an Android device
• 05.10 Test an application with multiple decisions

5.1 Creating an Android Project Using a List
(1 of 6)
• Lists are one of the most common
designs in mobile apps
− Scrollable
− Selectable
− Programmable to bring up the
next activity (screen)
• Figure 5-1 The City Guide Android
app

(2 of 6)
• Steps to complete the City Guide app:
1. Create a list using a ListView component.
2. Define an array to establish the items of the list.
3. Add the images used in the project.
4. Define an XML file to design a list.
5. Code a Switch decision structure to handle the selection of items.
6. Open an Android web browser to display a specified Uniform Resource Identifier
(URI).
7. Create multiple classes and XML layout files to display pictures of attractions.
209

(3 of 6)
• Beginning the City Guide App
− The opening screen of the City Guide app contains a vertical list of
attractions
− Selecting an item opens up a related web page or an image of the attraction
− The TableLayout view is similar to the ListView, but ListView allows you to
select each list row for further action
− With a ListView component, scrollbar is automatically displayed if there are
more items than the screen can display
210

(4 of 6)
Figure 5-4 Application
information for the new
Android project

(5 of 6)
Figure 5-5 Asset Studio dialog
box

(6 of 6)
Figure 5-6 Code to display
launcher icon

5.2 Adding a ListView Layout with XML Code
(1 of 2)
• Two ways to design a layout:
− Drag and drop components from the Palette into the emulator window
− Code the activity_main.xml file using XML code in the Layout Editor
• Studio provides an auto-complete feature to assist in writing XML
• For the City Guide project, the ListView component will be added by modifying
the activity_main.xml file

5.2 Adding a ListView Layout with XML Code
(2 of 2)
Figure 5-8 ListView layout

5.3 Creating an Array (1 of 2)
• Array: a container object that holds a fixed number of values of a single type
• An array variable can store more than one value
− You can avoid assigning a separate variable for each item in a list for a ListView
component
• Each individual item in an array that contains a value is called an element
• Arrays provide access to data by using a numeric index, or subscript
− Elements of the attraction array are accessed as attraction[0],
attraction[1], attraction[2], etc.

5.3 Creating an Array (2 of 2)
• Declaring an Array
− Declaration includes the array's data type and its name
− Sample arrays of numeric and character values:
int[] age={18,21,38,88};
double[] weather={72.3, 65.0, 25.7, 99.5};
char[] initials={'P','N','D'};
− Array of strings for the City Guide's ListView component:
String[] attraction = new String[]{"Art Institute of
Chicago", "Magnificent Mile", "Willis Tower", "Chicago
Bean", "Water Tower"};

5.4 Initializing a ListView Layout Component
(1 of 2)
• You use the Android ListView layout to display the array elements in a scrollable
list
• The list items are automatically inserted in the ListView component using a Java
Adapter that pulls content from a source such as an array or database

5.4 Initializing a ListView Layout Component
(2 of 2)
Figure 5-11 ListView layout
defined

5.5 Displaying an Array in the ListView with
an ArrayAdapter (1 of 3)
• An adapter provides a data model for the layout of a list and for converting the
array data into list items
• The ListView and ArrayAdapter work together to display a list
• The ArrayAdapter<String> supplies the String array data to the ListView
• The three parameters that follow ArrayAdapter refer to:
− The this class
− A generic layout (simple_list_item_1 for the City Guide)
− The array of list items

• Adapter code for the City Guide app:
ArrayAdapter<String> adapter = new ArrayAdapter<>(this,
android.R.layout.simple_list_item_1, android.R.id.text1,
attraction);
listView.setAdapter(adapter);
• Adding the Images to the Resources Folder
− Place images for the app into the res/drawable folder
− Remember to follow copyright laws that apply to any copyrighted images you
use

• Adding the String Table
− The City Guide app needs three strings for the ImageView component
descriptions
− These are added to the strings.xml file in the resvalues folder using the
Translations Editor

1. What is the name of the component that makes it easy to display a list of
items?
2. What are the individual items in an array called?
3. What does an adapter do?
4. Where do images need to be stored?

1. What is the name of the component that makes it easy to display a list of
items?
Answer: ListView component
2. What are the individual items in an array called?
Answer: elements
3. What does an adapter do?
Answer: It provides a data model for the layout of the list and for converting
the array data into list items
4. Where do images need to be stored?
Answer: In the res/drawable folder

5.6 Calling the setOnItemClick() Method
• setOnItemClick() is called when an item from the list is selected
• When an attraction in the list is selected, the position of the item is passed from
setOnItemClick() and evaluated with a decision structure
− The position parameter is assigned an integer value based on the index of
the array item selected (0, 1, 2, etc.)
• Code calling this method and onItemClick() method stub:
listView.setOnItemClickListener(new
AdapterView.OnItemClickListener()
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}

5.7 Creating a Decision Structure with a
Switch Statement (1 of 3)
• Switch statement: a decision structure that allows you to choose from many
statements based on an integer or single character (char) input
• Switch statement syntax:
switch(position){
case 0:
//statements that are executed if position == 0
break;
case 1:
//statements that are executed if position == 1
break;
default:
//statements that are executed if position != any of the
cases
}

• The switch keyword is followed by:
− An integer expression in parentheses
− Its cases, all enclosed in braces
• The case keyword is followed by a colon and a value
• Typically, the statement within a case ends with a break statement
− The break statement exits the Switch decision structure and continues with
the next statement
• If there is no matching case value, the (optional) default option is executed

Figure 5-18 Case statements

5.8 Understanding Android Intents
• A browser is launched with Android code using an intent
• Android intents send and receive activities and services
− They allow apps to talk to each other in a very simple way
• When the City Guide app sends an intent, the browser app handles the request
and opens the website

5.9 Launching a Browser from an Android
Device (1 of 6)
• Android phones have a built-in browser with an intent filter that accepts intent
requests from other apps
− The intent sends the browser a URI (Uniform Resource Identifier), a string
that identifies web resources
− URL (Uniform Resource Locator): a website address
− A URI is a URL with additional information necessary for gaining access to
the resources required for posting a web page
• ACTION_VIEW: a generic action you can use to send any request to get the
most reasonable action to occur
− The most common action performed on data

Device (2 of 6)
• Sample code for launching websites in an Android browser:
startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse
("http://artic.edu")));
• Adding Multiple Class Files
− Multiple classes are needed to display images on the screen when the user selects
Willis Tower, Chicago Bean, or Water Tower on the opening ListView component
− Classes must begin with a capital letter
− When you add a class by creating a new activity, a coordinating XML layout file with
the same name but a lowercase beginning letter is automatically created

Device (3 of 6)
• Designing XML Layout Files
− For the City Guide app, XML layout files must be designed to display an
ImageView component with an image source file
− To do this, you can drag an ImageView component into the emulater
− You can add its id attribute, adjust its constraint handles, and select a
description from the string table for its contentDescription attribute

Device (4 of 6)
Figure 5-25 The
activity_bean.xml file

Device (5 of 6)
• Coding the Multiple Class Files
− The City Guide app must launch the class files when the user selects an
item from the ListView component
− A startActivity() method for each case in the Switch statement opens the next
Activity, which in turn launches the appropriate XML layout that displays an
image
− Sample call to startActivity():
startActivity(new Intent(MainActivity.this,
Bean.class));

Device (6 of 6)
Figure 5-27 Complete code
for MainActivity.java class
[part b]

1. What Java method, which is called when an item in a ListView component is
selected, passes the position of the item for evaluation?
2. A Switch statement attempts to match an integer or character to one of its _____.
3. An Android intent that launches a browser identifies web resources by sending the
browser a(n) _____.
4. What is the most common action performed on data in an Android app?

1. What Java method, which is called when an item in a ListView component is
selected, passes the position of the item for evaluation?
Answer: setOnItemClick()
2. A Switch statement attempts to match an integer or character to one of its _____.
Answer: cases
3. An Android intent that launches a browser identifies web resources by sending the
browser a(n) _____.
Answer: URI (Uniform Resource Identifier)
4. What is the most common action performed on data in an Android app?
Answer: ACTION_VIEW

5.10 Testing an Application with Multiple
Decisions
• Make sure all the fields can gracefully handle any click or any value entered in any
Android app
• Click Run on the menu bar, then select Run to test the app in the emulator
• Testing an Android app is called usability testing
• In addition to the traditional tests of navigation and ease of use, Section 508
compliance is a third component to be tested
− The 1998 Amendment to Section 508 of the Rehabilitation Act spells out
accessibility requirements for individuals with certain disabilities
− For more details, refer to General Services Administration: Section 508 Report

Self-Assessment
1. How much of the Java code in the City Guide app project presented in
Chapter 5 was familiar versus unfamiliar to you? Describe your experience
working through the coding project and identify any related coding skills that
you would like to practice more.
2. Describe any previous coding experience you have with the Switch-case
decision structure. In what situations do you expect to use Switch statements
in your own coding projects?

Summary
Chapter objectives

241
Android Bootcamp
for Developers
Using Java, 4e
Chapter 6: Jam! Implementing
Audio in Android Apps

• 06.01 Create an Android project using a splash screen
• 06.02 Launch the splash screen before the MainActivity
• 06.03 Design a TextView component with a background image
• 06.04 Create a timer
• 06.05 Understand the life and death of an Activity
• 06.06 Assign class variables

• 06.07 Play music
• 06.08 Create a raw folder for music files
• 06.09 Play music with a MediaPlayer method
• 06.10 Start and resume music playback
• 06.11 Change the text attribute of a component
• 06.12 Change the visibility of a component

6.1 Creating an Android Project Using a
Splash Screen (1 of 5)
Figure 6-1 Aloha
Music Android app
Figure 6-2 Music
played in the
Android app

• The Aloha Music app displays a splash screen (opening screen) for five seconds, then opens a
second screen automatically
• Steps to complete the app:
− Create a splash screen with a timer.
− Design a TextView control with a background image.
− Initialize a TimerTask and a timer.
− Launch a second Activity.
− Design a second XML layout.
− Add music files to the raw folder.
− Initialize the MediaPlayer class.
− Play and pause music with a Button component.

• Beginning the Aloha Music App
− Many app splash screens include the program name, a brand logo, and/or
the author's name
− Android initializes its resources and loads necessary files while the splash
screen is displayed

Figure 6-3 Setting up the
Aloha Music project in the
New Project window

Figure 6-4 Adding the Splash
Activity (splash screen)

6.2 Launching the Splash Screen before the
MainActivity (1 of 3)
• By default, the MainActivity launches first
• To launch the SplashActivity (splash screen) first, you must modify the Android
Manifest file
− Move the first launch activity intent from MainActivity to SplashActivity
− Set android:exported property to "true"

Figure 6-5 Updating the
Android Manifest file

Figure 6-6 Launching the
Splash Activity first in the
Android Manifest file

6.3 Designing a TextView Component with a
Background Image (1 of 3)
• You use the TextView component's background attribute to specify a background image
− Can display an image or a solid-color fill
• The margins and gravity properties are used to place the text within the component
• For the Aloha Music app, you must:
− Add images to the drawable folder
− Enter text strings into the string table using the Translations Editor
− Add a TextView Component with a background image to the XML layout file for the
splash screen

Figure 6-8 Translations Editor

Figure 6-9 The
activity_splash.xml file
displays a TextView
component with a
background image

6.4 Creating a Timer (1 of 5)
• A timer in Java can:
− Execute a one-time task such as displaying an opening splash screen
− Perform a continuous process such as a morning wake-up call set to run at
regular intervals
• Timers use two Java classes, TimerTask and Timer
• Each time a timer runs, it runs in a single thread: a single sequential flow of
control within a program

• The first step in creating a timer is creating a TimerTask object:
TimerTask task = new TimerTask( ) {
@Override
public void run() {
}
• The TimerTask invokes a scheduled timer
• The TimerTask must implement a run() method that is called by the timer when
the task is scheduled for execution

Figure 6-11 The run() method

• Scheduling a Timer
− After a reference is included to the TimerTask class, a timer must be scheduled
− A delay timer is scheduled in milliseconds using the Timer class:
Timer opening = new Timer();
opening.schedule(task,5000);
 Line 1: the object named opening initializes a new instance of the Timer class
 Line 2: the schedule() method of the Timer class is called, passing in the name
of the variable that was initialized for the Timer class and the number of
milliseconds
 5,000 milliseconds = about 5 seconds

Figure 6-13 Timer scheduled
for 5 seconds

6.5 Understanding the Life and Death of an
Activity (1 of 7)
• Each activity has a life cycle—a series of actions from the beginning of an
Activity until its end
• When the activity begins, we use the onCreate() method
− Initializes the user interface with an XML layout
− Sets up the resources required to perform the Activity
• When the activity ends, we use the onDestroy() method
− Releases the Activity's resources to free up memory
• Four states of an Activity: active, paused, stopped, or dead

Activity (2 of 7)
Method Description
onCreate() The onCreate() method begins each Activity. This method also provides a Bundle containing
the Activity’s previously frozen state, if it had one.
onRestart() If the Activity is stopped, onRestart() begins the Activity again. If this method is called, it
indicates your Activity is being redisplayed to the user from a stopped state. The onRestart()
method is always followed by onStart().
onStart() If the Activity is hidden, onStart() makes the Activity visible.
onResume() The onResume() method is called when the user begins interacting with the Activity. The
onResume() method always follows onPause().
onPause() This method is called when an Activity is about to resume.
onStop() This method hides the Activity.
onDestroy() This method destroys the Activity. Typically, the finish() method (part of the onDestroy()
method) is used to declare that the Activity is finished; when the next Activity is called, the
method releases all the resources from the first Activity.

Activity (3 of 7)
• The finish() method is part of the onDestroy() method
− Called when the Activity is completed and should be closed
− Typically occurs directly before another Activity is launched
• In Figure 6-14:
− Rectangles represent methods you can implement to perform operations when the
Activity moves between states
− Colored ovals are the possible major states of the Activity
• In the Aloha Music app, onDestroy() is called from within the timer task's run() method
to destroy the SplashActivity before launching the second Activity

Activity (4 of 7)
Figure 6-14 Android life cycle

Activity (5 of 7)
Figure 6-15 After the finish( )
method is called

Activity (6 of 7)
• Launching the Next Activity
− An intent must request that the next Activity be launched
− For the Aloha Music app, the following line is added to the run() method after the
call to finish():
startActivity(new Intent(SplashActivity.this,
MainActivity.class));
• Designing the activity_main.xml File
− A second XML layout file is displayed when the onCreate() method is called within
MainActivity.java
− For the Aloha Music app, MainActivity.java uses the default Relative layout with two
ImageView and Button components

Activity (7 of 7)
Figure 6-19 The
activity_main.xml layout is
complete

1. What do you call an app's opening screen that displays a logo for a few
seconds?
2. Which type of object invokes a scheduled timer?
3. How many milliseconds equal approximately 1 second?
4. What are the four possible states of an Activity?
5. Which Android life cycle method will hide the Activity?

1. What do you call an app's opening screen that displays a logo for a few seconds?
Answer: Splash Screen
2. Which type of object invokes a scheduled timer?
Answer: TimerTask
3. How many milliseconds equal approximately 1 second?
Answer: 1,000
4. What are the four possible states of an Activity?
Answer: active, paused, stopped, or dead
5. Which Android life cycle method will hide the Activity?
Answer: onStop()

6.6 Assigning Class Variables (1 of 3)
• Local variables are declared by variable declaration statements within a
method
− Local variables effectively cease to exist when method execution is complete
• The scope of a variable refers to the variable’s visibility within a class
• Variables accessible from anywhere in a class have global scope
− When a variable is needed in multiple methods in a class, a global variable
is used
− Global scope variables are called class variables in Java

• For the Aloha Music app, class variables are defined for a Button, a
MediaPlayer, and an integer variable (playing) for each Button component's
onClick() method
• The onCreate() method opens the XML layout and defines two Button
components
− Each button has a setOnClickListener that implements the
Button.OnClickListener, creating an instance of OnClickListener and calling
the onClick() method, when the button is tapped
− The onClick() method responds to the user's action by playing or pausing the
song

Figure 6-23 Inserting the
second Button
OnClickListener stub

6.7 Playing Music
• Android phones and tablets include built-in music players
• Android includes a MediaPlayer class that can play both audio and music files
• Android allows you to play audio and video from several types of data sources:
media files stored in the app's resources, stand-alone files, an SD (Secure
Digital) memory card, a data stream from the Internet
• .mp3 is the most common supported audio file type, but .wav, .ogg, and .midi
are typically supported by most Android hardware
• Codec: a computer technology used to compress and decompress audio and
video files

6.8 Creating a Raw Folder for Music Files
• Music files are typically stored in a new resource directory called raw
− A subfolder created in the res folder
• The raw resource directory must be created before music files are added to the
project
• In Android Studio, right-click the res folder and select New, then Android
resource directory to add the raw folder

6.9 Playing Music with a MediaPlayer Method
(1 of 2)
• A MediaPlayer class provides the methods to control audio playback on
Android devices
− Provides access to built-in MediaPlayer services for playing audio and video
files
• For the Aloha Music app, two MediaPlayer class variables are declared and an
instance of the MediaPlayer class is assigned to each

6.9 Playing Music with a MediaPlayer Method
(2 of 2)
Figure 6-26 MediaPlayer
instance statements

6.10 Starting and Resuming Music Playback
(1 of 2)
• The playback state of the MediaPlayer determines whether an audio file is playing
− start() begins media playback
− pause() pauses media playback
− stop() stops media playback
• Android does not have a method for determining the current state of the MediaPlayer
• For the Aloha Music app, an integer variable named playing is used to track the state
− A Switch decision structure changes the value of playing each time the user taps
the playback/pause button

6.10 Starting and Resuming Music Playback
(2 of 2)
Figure 6-27 Variable named
playing is set to 0

6.11 Changing the Text Attribute of a
Component (1 of 2)
• When a Button component is used as a toggle button, its text should be
changed to correspond with its functionality when it is tapped
• You can change the text attribute using Java code by calling the setText()
method:
button1.setText("Pause Ukulele Song");
• For the Aloha Music app, this method is added to the case statements of each
Button component's Switch decision structure

6.11 Changing the Text Attribute of a
Component (2 of 2)
Figure 6-28 The setText( )
method changes the button
text in both case statements

6.12 Changing the Visibility of a Component
(1 of 4)
• Visibility attribute: the Java attribute that determines whether a component is
displayed on the emulator
− Set to be visible by default
− Code to hide a component:
button2.setVisibility(View.INVISIBLE);
− Code to display a component:
button2.setVisibility(View.VISIBLE);
• For the Aloha Music app, calls to setVisibility() are added to the Switch decision
structure to make the opposing play button disappear

(2 of 4)
Figure 6-30 The setVisibility()
method changes the visibility
of the Button component

(3 of 4)
Figure 6-31 Completed code
for MainActivity.java

(4 of 4)
• Running and Testing the Application
− Click Run  Run on the Android Studio menu bar to save and test the
application in the emulator
− The splash screen should display for five seconds
− Then the activity_main layout screen should open
− Test both buttons to ensure they operate as expected

1. Which kind of variable is visible to all methods within a class?
2. What goes in the raw folder?
3. Why do we need Switch statements in the Aloha Music app?
4. What are the two possible values for the visibility attribute?

1. Which kind of variable is visible to all methods within a class?
Answer: global variable or class variable
2. What goes in the raw folder?
Answer: audio or video files
3. Why do we need Switch statements in the Aloha Music app?
Answer: Using Switch statements for the Button components allows us to
easily perform the set of actions appropriate for the current state of the
MediaPlayer (the case) when a button is tapped.
4. What are the two possible values for the visibility attribute?
Answer: visible and invisible

Self-Assessment
1. As an app consumer, have you noticed splash screens and/or background
music in apps that you frequently use? If so, what do you think of these
features?
2. To what extent, and in what contexts, do you anticipate using the TimerTask,
Timer, and MediaPlayer classes in apps that you develop professionally?
3. Attempt to map the user flow of one of your favorite apps to the Android life
cycle depicted in Figure 6-14. How easy or difficult is it to recognize the app's
activities and follow their state changes?

Summary
Chapter objectives

288
Android Bootcamp
for Developers
Using Java, 4e
Chapter 7: Reveal! Displaying
Pictures in a GridView

• 07.01 Create an Android project using a GridView component
• 07.02 Add a GridView to display a two-dimensional grid of images
• 07.03 Add the ImageView component in XML code
• 07.04 Create an array for images
• 07.05 Instantiate the GridView and ImageView components
• 07.06 Use a setAdapter with an ImageAdapter

• 07.07 Code the OnItemClickListener
• 07.08 Code a custom toast notification
• 07.09 Display the setImageResource image
• 07.10 Define a Context resource
• 07.11 Determine the length of an array
• 07.12 Code the getView() method

GridView Component (1 of 3)
• The GridView layout tool shows items in a two-dimensional scrolling grid
• Endangered Species app
− Users can scroll an image grid by flicking their fingers across a horizontal list
of thumbnail-sized pictures
− To view a larger image of one of the endangered animals, users can tap a
thumbnail
− A toast notification is used to display the species number for the selected
image

Figure 7-2 Panda image
selected in the grid

• To create this app, you must:
− Add a GridView component and an
ImageView component to the
emulator
− Update the XML code for an
ImageView component not linked to a
particular image
− Place six images in a drawable folder
− Define an array to hold the image
files
− Instantiate the GridView and
ImageView components
− Create an ImageAdapter class
− Display a custom toast message
− Display the selected image
− Customize the ImageAdapter class
− Define the layout using the getView()
method

7.2 Adding a GridView to Display a Two-
Dimensional Grid of Images (1 of 4)
• A View container is a rectangular area of the screen that displays an image or text
object
− Can include layouts such as GridView, RadioGroup, ScrollView, TabHost, and
ListView
• The GridView container displays a horizontal list of objects
− This layout can be used to build applications that show elements in a table or grid
− Photos in a grid can be sized as thumbnail images or full-screen images
− Photos can be stored in the drawable folders, in a phone’s storage, or on a website
such as Picasa

GridView Attribute Name Description
android:columnWidth Specifies the fixed width for each column of the grid
android:numColumns Defines the number of columns in the grid
android:horizontalSpacing Defines the default horizontal spacing between columns in the grid
android:verticalSpacing Defines the default vertical spacing between rows in the grid

Figure 7-4 GridView
component in the emulator
for the Endangered Species
project

Figure 7-6 Customized
GridView XML code

7.3 Adding the ImageView Component in XML
Code (1 of 4)
• Typically, you add an ImageView component by dragging it onto the emulator
• If an image should appear in the ImageView component only after a user event,
you can prevent an image from being automatically assigned to the component
by entering the XML code for it instead
− The component is coded in activity_main.xml
− The source display is coded in MainActivity.java
• The ImageView's content description is entered into the String table
• The image files for display are placed in the drawable folder

Code (2 of 4)
Figure 7-7 ImageView XML
code

Code (3 of 4)
Figure 7-8 Adding a String
value

Code (4 of 4)
Figure 7-9 Images copied

7.4 Creating an Array for Images (1 of 2)
• The images for the GridView must be referenced
in the code and assigned to an array
• Arrays provide access to data by using a numeric
index (subscript) to identify each element
• Syntax:
Integer[] Animals =
{R.drawable.elephant,
R.drawable.gorilla,
R.drawable.leopard, R.drawable.panda,
R.drawable.polar, R.drawable.rhino};
Element of Array Image File
Animals[0] elephant.png
Animals[1] gorilla.png
Animals[2] leopard.png
Animals[3] panda.png
Animals[4] polar.png
Animals[5] rhino.png

7.4 Creating an Array for Images (2 of 2)
referenced

7.5 Instantiating the GridView and ImageView
Components
• The code to instantiate the GridView assigns the name gvAnimals to the
component created in activity_main.xml
• Java code syntax for instantiating the GridView:
GridView grid = findViewById(R.id.gvAnimals);
• Java code syntax for instantiating the ImageView, which is assigned as a class
variable:
final ImageView pic = findViewById(R.id.ivLarge);

7.6 Using a setAdapter with an ImageAdapter
(1 of 3)
• A setAdapter provides a data model for the GridView layout
− This adapter helps to set the data from an array list or a database to the
items of the grid
• Java code syntax to instantiate a custom BaseAdapter class called
ImageAdapter and apply it to the GridView using setAdapter():
grid.setAdapter(new ImageAdapter());

(2 of 3)
Figure 7-14 Instance of the
ImageAdapter class

(3 of 3)
Figure 7-15 ImageAdapter
class and auto-generated
code

1. What is the name of the component that displays a horizontal list of objects?
2. What is a View container?
3. What is each item in an array called?
4. Where should photos you use in an Android app project be stored?
5. The data model for a GridView layout is provided by a(n) _____.

1. What is the name of the component that displays a horizontal list of objects?
Answer: GridView component
2. What is a View container?
Answer: A rectangular area of the screen that displays an image or text object.
3. What is each item in an array called?
Answer: element
4. Where should photos you use in an Android app project be stored?
Answer: drawable folder
5. The data model for a GridView layout is provided by a(n) _____.
Answer: setAdapter

7.7 Coding the OnItemClickListener (1 of 4)
• The OnItemClickListener awaits user interaction within the GridView component
• The onItemClick() method is executed by the OnItemClickListener when the
user touches an image within the GridView component
− Has four arguments: parent, view, position, and id
• ListView and GridView components enable the Android device to monitor for
click events

• Java syntax for the onItemClick() method:
grid.setOnItemClickListener(new OnItemClickListener( ) {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
}
}};
}

Argument Purpose
AdapterView<?>
parent
The AdapterView records “where” the user actually touched the screen in the argument
variable parent. In other words, if the app has more than one View component, the
AdapterView determines if the user touched the GridView component or another
component in the application.
View view The View parameter is the specific View within the item that the user touched. This is the
View provided by the adapter.
int position This is one of the most important portions of this statement in the chapter project. The
position argument is an integer value that holds the position of the View in the adapter.
For example, if the user taps the elephant picture, the integer value of 1 is stored in
position because the elephant picture is the second image in the Animals array.
long id The GridView component is displayed across multiple rows of the Android device. The
argument id determines the row id of the item that was selected by the user. This is
especially useful for a GridView component that has multiple rows in the layout.

Figure 7-16 GridView
OnItemClickListener

7.8 Coding a Custom Toast Notification
(1 of 2)
• Toast notifications display a temporary message to the user
• Toast notification code used in earlier chapters:
Toast.makeText(MainActivity.this, "Typical Toast Message",
Toast.LENGTH_SHORT).show();
• When you use a toast notification in an onItemClick() method rather than directly in the
MainActivity, the reference to MainActivity.this creates an error
• In Android programs, you can place the getBaseContext() method in another method
(such as onItemClick()) that is triggered only when the user touches the GridView
component
• If you do, the getBaseContext() method obtains a Context instance

7.8 Coding a Custom Toast Notification
(2 of 2)
• Figure 7-17 Toast message displayed when the user
selects the leopard image
• Notice that even though the leopard is in position
Animals[2] in the Animals array, the custom toast
message states “Selected Species 3”
− Array position 2 is really the third image because the
array values begin with 0
• Java syntax for this toast notification:
Toast.makeText(getBaseContext(),
"Selected Species " + (position + 1),
Toast.LENGTH_SHORT).show();

7.9 Displaying the setImageResource Image
(1 of 2)
• When the user selects an animal picture, a toast message appears with an
ImageView component that displays the selected image
• An ImageView component is defined either by the android:src attribute in the
XML element or by the setImageResource(int) method
• Java syntax for the setImageResource() method:
pic.setImageResource(Animals[position]);

7.9 Displaying the setImageResource Image
(2 of 2)
• Customizing the ImageAdapter Class
− The ImageAdapter class was called with this line of code: gr.setAdapter(new
ImageAdapter (this));
− The ImageAdapter class determines the layout of the GridView
− The context and images of the GridView need to be referenced within the
ImageAdapter class
− The tasks to complete inside the ImageAdapter class:
 Manage the layout of the GridView
 Connect the data sources from the array for display within the GridView
component

7.10 Defining the Context of the
ImageAdapter Class (1 of 3)
• A Context variable is used to load and access resources for the application
• Constructors are used to initialize the instance variables of an object
− A constructor is similar to a method but always has the same name as the
class whose instance members it initializes
− A constructor does not contain a return type
• When we call a constructor, we often have to pass a Context, and we often use
the Java command "this" to pass the activity Context to the application Context

• Java code that initializes the class variable named Context so it can hold each
image in the GridView temporarily before it is displayed:
private Context context;
public ImageAdapter(Context c){
context=c;
}

Figure 7-22 Passing the
Context to the ImageAdapter
Class

7.11 Calculating the Length of an Array
• The length of an array is determined by the number of elements in the array
• When the ImageAdapter class is called, the getCount() method determines how many
pictures should be displayed in the GridView
− getCount() calls length(), which returns the number of pictures in the array:
public int getCount() {
return Animals.length;
}
− The Java length() method returns an integer value for any string or array
• A Java method is a series of statements that perform some repeated task

7.12 Coding the getView() Method (1 of 6)
• The getView() method uses a Context to create a new ImageView instance that
temporarily holds each image displayed in the GridView
• The returned pic is a scaled, resized image, ready to display in the GridView
component
• getView() method Java code:
public View getView(int position, View convertView, ViewGroup
parent){
pic = new ImageView(context);
pic.setImageResource(Animals[position]);
pic.setScaleType(ImageView.ScaleType.FIT_XY);
pic.setLayoutParams(new GridView.LayoutParams(330,300));
return pic;
}

• Scaling keeps or changes the aspect ratio of the image within the ImageView
component
ScaleType Option Meaning
ImageView.ScaleType.CENTER This option centers the image within the View type but does not
change the aspect ratio (no scaling).
ImageView.ScaleType.CENTER_CROP This option centers the image within the View type and scales
the image uniformly, maintaining the same aspect ratio.
ImageView.ScaleType.FIT_XY This option scales the image to fit the View type. The aspect
ratio is changed to fit within the component.

• After the image is scaled, the GridView images are resized to fit the custom layout
• LayoutParams are set to GridView.LayoutParams(330,300)
− 330 pixels across the image
− Height of 300 pixels
• The last statement in the getView() method, return pic;, must return the instance
of the ImageView component named pic to display in the GridView component
− Save the app, run it in the emulator, and test its functionality

Figure 7-28 Complete code of
MainActivity.java (part 1)

1. What do you use to initialize the instance variables of an object?
2. A series of Java statements that perform some repeated task is called a(n) _____.
3. What method does the OnItemClickListener execute when the user touches its
associated component?
4. What change to the Java code for a typical toast notification must you make to use a
toast message within an onItemClick() method?
5. What does the getView() method do?

(1 of 2)
1. What do you use to initialize the instance variables of an object?
Answer: constructor
2. A series of Java statements that perform some repeated task is called a(n)
_____.
Answer: method
3. What method does the OnItemClickListener execute when the user touches its
associated component?
Answer: onItemClick()

(2 of 2)
4. What change to the Java code for a typical toast notification must you make to
use a toast message within an onItemClick() method?
Answer: You must replace MainActivity.this with a Context class called
getBaseContext().
5. What does the getView() method do?
Answer: It uses a Context to create a new ImageView instance that
temporarily holds each image displayed in the GridView.

Self-Assessment
1. How do you anticipate using the GridView component (or similar Android
layout tools) in your own apps? Did the use of this component in the
Endangered Species project give you any inspiration for your own app
projects?
2. Do you enjoy creating custom classes such as the ImageAdapter used in the
Endangered Species app? Or would you prefer to stick to classes provided in
the Android libraries? Explain the reasons for your preference.

Summary
Chapter objectives

333
Android Bootcamp
for Developers
Using Java, 4e
Chapter 8: Design! Using a
DatePicker on a Tablet

• 08.01 Create an Android app on a tablet
• 08.02 Design a tablet app with modern design principles
• 08.03 Add an Android virtual device for the tablet
• 08.04 Design a tablet table layout
• 08.05 Add date, time, and clock components

• 08.06 Create a Calendar class
• 08.07 Select the date from the DatePickerDialog
• 08.08 Add the onDateSet() method
• 08.09 Display the date using the getTime() method
• 08.10 Add an Android theme

Introduction
• Android Apps not limited to phones
• Tablets are used to:
− Connect to the Internet
− Play games
− Use social media
− Check e-mail
− And more

8.1 Creating an Android App on a Tablet
(1 of 2)
• Figure 8-2 DatePicker calendar component in a dialog box
• Figure 8-3 TextView component displays reservation

8.1 Creating an Android App on a Tablet
(2 of 2)
• Steps required to create the Sailing Adventures application:
1. Add an Android virtual device specifically designed for tablets
2. Add the images used in this project
3. Change the theme and icon for the tablet display
4. Create a custom XML file with a table layout
5. Add and initialize TextView components and the Button component
6. Initialize a DatePickerDialog with the current date and listen for the user to select
a date
7. Return the selected date
8. Display the selected reservation date in the TextView component

8.2 Designing a Tablet App with Modern
Design Principles (1 of 2)
• Native applications are programs locally installed on a specific platform (phone
or tablet)
• An emulated application is converted in real time to run on a variety of
platforms (various screens)
• Native Android tablet apps create an optimal user experience based on the
most common tablet screen sizes
− Between 7.3 and 10.1 inches (diagonally)
− 2560 × 1600 pixel resolution and 16:10 screen ratio
− iPad Air specs: 9.7 inches, 2048 × 1536 pixels, 4:3 screen ratio

8.2 Designing a Tablet App with Modern
Design Principles (2 of 2)
• Design Best Practices for Tablets
− Understand the use case scenarios for tablets
− Keep screens uncluttered and use large-enough components
− Make the design simple and the app intuitive
− Leave out “cool” interactions that distract the user
− Use flexible dimension values such as dp and sp instead of px or pt
− Provide higher-resolution resources for screen densities (DPI)
− Create a unique experience for phone and tablet designs
− Use larger fonts than with a phone app

8.3 Adding an Android Virtual Device for the
Tablet (1 of 5)
• An API platform and Android virtual devices (ADVs) are necessary for
developing tablet apps
• The minimum required SDK should be set to API 13: Android 3.2 (Honeycomb)
to cover the oldest Android tablets
• The target SDK is automatically set to cover the most recent versions of Android
tablets
• Each Android device configuration is stored in an AVD
• First steps to create the Sailing Adventures app: create the new project and add
the appropriate AVD configuration

Tablet (2 of 5)
Figure 8-5 New Project
window

Tablet (3 of 5)
Figure 8-6 The
activity_main.xml file is
displayed to select a tablet
device

Tablet (4 of 5)
Figure 8-8 Selecting a Nexus
10 virtual device

Tablet (5 of 5)
• Creating the String Table
− The sailboat image for the Sailing Adventures app must be added to the
drawable folder
− The text values for the components must be entered into the strings.xml file

8.4 Designing a Tablet Table Layout (1 of 7)
• The LinearLayout and TableLayout
elements can be combined to create
a simple, clean interface for a table
app
• TableLayout is composed of
TableRow components—one for each
row
• You add a view to a row to create
additional columns
sail.png Title
Day trip description
Reservation button
Reservation date after selection

• The padding property can be used to offset the content of the component by a
specific number of pixels
• The typeface property sets the style of the text to a font family such as
monospace, sans serif, or serif
• The Sailing Adventures app's TableLayout includes four rows:
− Two stacked TextView components
− One Button component
− One more TextView component

• XML syntax for the app's structure:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
<ImageView />
<TableLayout
<TableRow>
<TextView />
</TableRow>
<TableRow>
<TextView />
</TableRow>
<TableRow>
<Button />
</TableRow>
<TableRow>
<TextView />
</TableRow>
</TableLayout>
</LinearLayout>

Figure 8-13 LinearLayout in
XML code

component in XML code

Figure 8-15 TableLayout XML
code for first two TableRows

Figure 8-16 TableLayout XML
code for last two TableRows

1. What is the difference between native applications and emulated applications?
2. What is the name of the first Android operating system that was designed to support
tablets?
3. What property is used to offset the content of a component by a specific number of
pixels?
4. How are rows and columns created in an app with a TableLayout?

1. What is the difference between native applications and emulated applications?
Answer: Native applications are installed locally on a platform whereas emulated
applications are converted in real time through a browser.
2. What is the name of the first Android operating system that was designed to support
tablets?
Answer: Android Honeycomb 3.2 (API 13)
3. What property is used to offset the content of a component by a specific number of
pixels?
Answer: padding
4. How are rows and columns created in an app with a TableLayout?
Answer: Rows are created by adding TableRow XML elements, and columns are
added by adding views to the TableRow elements.

8.5 Using Date, Time, and Clock Components
(1 of 3)
• Android provides ready-to-use components called dialogs or dialog boxes that enable
the user to pick a valid time or date
• A DatePicker component is displayed in a dialog box to help the user determine and
choose a valid date
− Similar components: TimePicker, CalendarView, AnalogClock
• All Android devices keep a numeric representation of the system’s current date and
time, which can be displayed in multiple formats
• Creating a component to enter the date is crucial because requiring users to type the
date in a text box can lead to multiple errors, including incorrect
formats or typos

(2 of 3)
• Instantiating the Components
− The tvReservation TextView component is referenced in multiple methods,
so this instantiation must be declared as a class variable
− The TextView component, Button component, and Button OnClickListener
must all be instantiated

(3 of 3)
Figure 8-20 The onClickListener()
method for the button

8.6 Creating a Calendar Class (1 of 4)
• The Android system date is accessed by using the Calendar class, which
converts information between a Date object and a set of integer fields such as
YEAR, MONTH, and DAY_OF_MONTH
• The getInstance() method returns a calendar date or time based on the system
settings
• The date constants in this class are YEAR, MONTH, and DAY_OF_MONTH
− DAY_OF_YEAR displays the day number of the current year
• Syntax for creating an instance of the Calendar class named c:
Calendar c = Calendar.getInstance();

• Date Format
− The DateFormat Java class formats the date into a String value
− Syntax: DateFormat fmtDate = DateFormat.getDateInstance();
• DatePickerDialog Input
− The DatePickerDialog allows you to select a date from a DatePicker View
 Other dialog boxes include the TimePickerDialog and ProgressDialog
− The field manipulation method called get accesses the system date or time
− set changes the current date or time

• DatePickerDialog Input (continued)
− Syntax for launching the DatePickerDialog in the onClick() method and
passing it the values for the current year, month, and day:
public void onClick(View v) {
new DatePickerDialog(MainActivity.this, d,
c.get(Calendar.YEAR), c.get(Calendar.MONTH),
c.get(Calendar.DAY_OF_MONTH)).show();
}
− The variable d is assigned later to the user-selected date

Figure 8-23 DatePickerDialog
launched within the onClick()
method

8.7 Selecting the Date from the
DatePickerDialog
• To enable access to the system date, the variables are initialized and displayed
for the current YEAR, MONTH, and DAY_OF_MONTH
• Next, the DatePickerDialog component must await user interaction via an
OnDateSetListener named d, which listens for a callback indicating that the user
has filled in the reservation date
• Syntax for creating the onDateSetListener:
DatePickerDialog.OnDateSetListener d = new
DatePickerDialog.OnDateSetListener() {
}

1. What are some time and date components that are available in Java?
2. A(n) _____ listens for a callback indicating that the user has filled in a date in a
DatePickerDialog.
3. Calling _____ on a Calendar instance accesses the device system date’s month.
4. Why is using a component designed specifically to allow a user to enter a date preferable to
using a text box?
5. What class is responsible for converting information between a Date object and a set of
integer fields such as YEAR, MONTH, and DAY_OF_MONTH?

1. What are some time and date components that are available in Java?
Answer: TimePicker, DatePicker, CalendarView, Chronometer, and AnalogClock
2. A(n) _____ listens for a callback indicating that the user has filled in a date in a
DatePickerDialog.
Answer: OnDateSetListener
3. Calling _____ on a Calendar instance accesses the device system date’s month.
Answer: get(Calendar.MONTH)
4. Why is using a component designed specifically to allow a user to enter a date preferable to
using a text box?
Answer: A calendar component ensures the user’s entry is a valid date.
5. What class is responsible for converting information between a Date object and a set of
integer fields such as YEAR, MONTH, and DAY_OF_MONTH?
Answer: Calendar class

8.8 Adding the onDateSet() Method
• When the user selects a date from the DatePickerDialog, the onDateSet()
method automatically obtains the date selected by the user
• Syntax for the onDateSet() method:
public void onDateSet(DatePicker view, int year,
int monthOfYear, int dayOfMonth) {
c.set(Calendar.YEAR, year);
c.set(Calendar.MONTH, month);
c.set(Calendar.DAY_OF_MONTH, dayOfMonth);
}

8.9 Displaying the Date Using the getTime()
Method (1 of 3)
• The getTime() method returns the time value in the Date object
• Syntax for displaying the user-selected date in the TextView object using the
getTime() method:
reservation.setText("Your reservation is set for " +
Date.format(c.getTime( )));

Method (2 of 3)
Figure 8-26 Completed Java
code for Sailing Adventures
app, Part 1

Method (3 of 3)
Figure 8-26 Completed Java
code for Sailing Adventures
app, Part 2

8.10 Adding an Android Theme (1 of 4)
• A theme is a style applied to an Activity or an entire application
• Themes are Android’s mechanism for applying a consistent style to an app or
Activity on any device
• The style specifies the visual properties of the elements that make up a user
interface, such as color, height, padding, and font size
• Themes alter features such as the background wallpaper and may be used to
display (or not) a title bar or action bar
• Every UI element in the application should follow the app's parent theme

Figure 8-28 Android theme
examples

• Changing a Theme: You must define themes in the themes.xml or styles.xml file in the
values subfolder
• Running and Testing the Application: Save and test the application in the tablet
emulator
Theme Code in themes.xml Description
<style name="AppTheme" parent="Base.Theme.AppCompat"> Black background, gray title bar
<style name="AppTheme" parent="Base.Theme.AppCompat.Light"> White background, gray title bar
<style name="AppTheme" parent="Theme.Design.NoActionBar"> White background, no title bar

Figure 8-29 The themes.xml
file

Self-Assessment
1. Which of the best practices for tablet design listed in Chapter 8 do you think
are most important to ensuring a good user experience? Did any of these
guidelines surprise you?
2. How do you typically keep up to date with best practices for design in your
own software development? Consider how you might further improve your
skills in this area.
3. Have you used any of the Java classes/methods for handling dates and times
discussed in this chapter in other projects? If so, compare their application in
your project(s) with the way they are used in the Sailing Adventures app.

Summary
Chapter objectives

375
Android Bootcamp
for Developers
Using Java, 4e
Chapter 9: Customize!
Navigating with a Primary/Detail
Flow Activity on a Tablet

Chapter Objectives
• 09.01 Describe responsive design for Android apps
• 09.02 Create an Android tablet project using an application template
• 09.03 Use the Primary/Detail Flow template
• 09.04 Modify the Primary/Detail Flow template
• 09.05 Design an XML TableLayout
• 09.06 Add a WebView component
• 09.07 Customize the content of the sample template file
• 09.08 Display a custom layout in the detail pane

9.1 Understanding Responsive Design
(1 of 5)
• Design elements such as fluid grids and flexible images can adapt to various
screen sizes
• The Bike and Barge application project relies on built-in templates that use the
best presentation mode based on the size of the device
− Multipane tablet interface
− Items from a list in the left pane can be tapped to make the selected content
display in the right pane

(2 of 5)
Figure 9-2 Selecting Photos in
the left pane

(3 of 5)
• Steps to create the Bike and Barge app:
− Create an application with a Primary/Detail Flow template
− Add the images to the drawable folder
− Add text to the String table
− Create the photos.xml file using a TableLayout for the detail pane of the first
list item
− Create the tour.xml file for the detail pane of the second list item
− Change the default TextView component to a WebView component

(4 of 5)
• Steps to create the Bike and Barge app (continued):
− Update the AndroidManifest file to include an Internet permission
− Customize the PlaceholderContent class to display the item list
− Customize the PlaceholderContent class to connect the app to the website
− Modify the ItemDetailFragment.java class to:
 Display photos.xml in the detail pane
 Display tour.xml in the detail pane
 Display a website in a browser

(5 of 5)
• Creating Apps with Responsive Design
− Responsive design: an approach to designing apps and websites that
provides an optimal viewing experience across as many devices as possible
− Android Studio provides responsive design templates, which allow you to
build an app once but display it on multiple devices
− Thanks to the use of one of these templates, the Bike and Barge app can be
run on a smartphone emulator without code changes
 There, the app runs as two Activities instead of two panes

9.2 Creating an Android Tablet Project Using
an Application Template (1 of 2)
• Application templates are used to create basic Android applications that can
immediately be run and tested on an Android device of any size
• Android templates are available when you create a new Android project
− The Bike and Barge app uses the Primary/Detail Flow application template
− A similar template is the Navigation Drawer Activity

9.2 Creating an Android Tablet Project Using
an Application Template (2 of 2)
Figure 9-6 Android
application templates

9.3 Using the Primary/Detail Flow Template
(1 of 2)
• The Primary/Detail Flow template creates an adaptive, responsive layout for a
set of list items and associated detail content
− An interface design concept in which a list of items (the Primary list) appears
in a narrow vertical pane along the left edge of the screen
− The item details are displayed on the right side of the tablet screen in the
wider detail pane
− Referred to as a two-pane layout
• To begin creating the Bike and Barge app, you start a new project and select the
Primary/Detail Flow template

9.3 Using the Primary/Detail Flow Template
(2 of 2)
Figure 9-9 Creating the Bike
and Barge Android app

9.4 Modifying the Structure of the
Primary/Detail Flow Template (1 of 3)
Figure 9-10 Template code
files in the java folder

• Java Files
− ItemDetailFragment.java
 Displays the fragment_item_detail.xml layout file
 Can be customized to determine which detailed items to display
− ItemDetailHostActivity.java: displays the activity_item_detail.xml layout file if
a smartphone is detected
− ItemListFragment.java: displays the activity_item_list.xml layout file

• Layout Files
− activity_item_detail.xml: used by the app to display the FrameLayout
instance when a smartphone is detected
− fragment_item_detail.xml: used by the app when a smartphone is detected
to display the Primary list fragment
− fragment_item_detail.xml (sw600dp): used when a tablet is detected; the
app is displayed in a two-pane layout containing both the Primary item list
fragment and the item detail container
− item_list_content.xml: displays the detail pane using the onCreateView()
method when a smartphone or a tablet is detected

9.5 Designing an XML TableLayout (1 of 6)
• Before designing the XML layouts, first place the three required images in the drawable
folder and then reference them in the photos.xml layout
• The String table is responsible for the text displayed in the app
− The template's String table has two initial strings:
 The first string is displayed in the title bar of the tablet
 The second string is displayed in the title bar of a smaller device such as a
smartphone
− Other strings required for the app can be added to this table
• photos.xml uses a TableLayout consisting of three rows

Figure 9-12 String table for
the Bike and Barge app

Figure 9-15 First row of the
TableLayout

Figure 9-16 Second and third
rows of the TableLayout

Figure 9-17 Completed
TableLayout in photos.xml in
Design view

• Creating a TextView XML Layout for the Second List Item
− The second list item of the Bike and Barge app contains two TextView components
within a LinearLayout
− First TextView component XML code (the second is very similar):
<TextView
android:id="@+id/tvTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvTitle"
android:textSize="50sp"
android:paddingStart="50sp"
android:paddingBottom="60sp" />

9.6 Creating a WebView XML Layout (1 of 2)
• Webview object: a View component that displays webpages
• Permission: a restriction that limits access to a part of the code or to data on
the device
• Code syntax for requesting permission to connect to the Internet within the
AndroidManifest.xml file:
<uses-permission android:name="android.permission.INTERNET"
/>
• Code syntax for enabling cleartext (disabled by default):
android:usesCleartextTraffic="true"

9.6 Creating a WebView XML Layout (2 of 2)
• The TextView component code must be modified to replace it with a WebView
component in the fragment_item_detail.xml layout file (sw600dp and regular
versions)
• WebView component syntax:
<WebView
android:id="@+id/item_detail"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context= ".ItemDetailFragment" />

1. What does Android Studio do when you create a project using the
Primary/Detail Flow template?
2. What kind of template files are “activity_item_detail,” “fragment_item_detail,”
and “item_list_content”?
3. What code do you include in the AndroidManifest.xml file to give permission to
an app to access the Internet?
4. To provide an optimal viewing experience across as many devices as possible
for your Android application, you should implement _____ principles.

(1 of 2)
1. What does Android Studio do when you create a project using the
Primary/Detail Flow template?
Answer: Studio adds a group of Java and XML layout resource files, each
with a specific purpose, to the app project automatically.
2. What kind of template files are “activity_item_detail,” “fragment_item_detail,”
and “item_list_content”?
Answer: XML layout files

(2 of 2)
3. What code do you include in the AndroidManifest.xml file to give permission to
an app to access the Internet?
Answer: <uses-permission android:name="android.permission.INTERNET" />
4. To provide an optimal viewing experience across as many devices as possible
for your Android application, you should implement _____ principles.
Answer: responsive design

9.7 Customizing the Content of the Sample
Template File
• The Java class file PlaceholderContent.java (in the placeholder folder) provides
sample content to display in the UI of the template
• This class can be customized or replaced as needed
• Code syntax for using the addItem command to display list items in the left pane
of the tablet display/first Activity on a smartphone:
// Add some sample items.
addItem(new PlaceholderItem("1", "Photos", ""));
addItem(new PlaceholderItem("2", "Tour", ""));
addItem(new PlaceholderItem("3", "Website",
"https://bikebarge.com"));

9.8 Displaying the Custom Layout in the
Detail Pane (1 of 6)
• A fragment is a piece of an application’s user interface or behavior that can be placed
in an Activity
− Fragments are essentially a sub-Activity hosted inside another Activity
• To determine if two String objects match exactly:
− Use the .equals() method, not the == operator
− The == operator compares if two objects are exactly the same object
− Two strings may be different objects but have the same exact characters
− The .equals() method is used to compare strings for equality

• Java syntax used to compare the value of a string:
if (mItem != null) {
if (mItem.id.equals("1"))
}
• Code within ItemDetailFragment.java to display a custom XML layout file named
photos.xml in the detail pane:
rootView = inflater.inflate(R.layout.photos, container, false);
− Three arguments: The first part displays the XML layout, the second part applies
the layout parameters to the container, and the third part is false, a Boolean type
declaring that the layout was already passed to the container

• Syntax used to display the webpage URL with the variable named item_url
within the WebView component:
((WebView)
rootView.findViewById(R.id.item_detail)).loadUrl(mItem.cont
ent);
• We want the page to load in the right pane, not in a separate screen in the
Chrome browser (the default), so we create an instance of the WebViewClient
class and assign it the shouldOverrideUrlLoading() callback method
• We code four conditional If statements to display the XML layout and the
webpage within the detail pane

Figure 9-27
ItemDetailFragment.java class
customized for the third list
item

− Click the Run app button on the Standard toolbar, select the Nexus 10
emulator to test the application, and then click the OK button
− Unlock the emulator (if necessary)
− Test each list item to ensure it works as intended
− You must have Internet connectivity to open the webpage and enough
memory available to handle the app's connection to the Web
− If you have trouble with the Nexus 10 emulator, the 10.1-inch WXGA tablet
emulator is an alternative

1. What is a fragment in the context of an Android app?
2. To determine if two String objects contain the same characters, you use the
_____; to determine if they are the same object, you use the _____.
3. I am a method with three arguments. The first part displays an XML layout, the
second part applies the layout parameters to the container, and the third part
is false, a Boolean type declaring that that layout was already passed to the
container. Who am I?

1. What is a fragment in the context of an Android app?
Answer: A piece of an application’s user interface or behavior that can be placed in
an Activity. A fragment is essentially a sub-Activity hosted inside another Activity.
2. To determine if two String objects contain the same characters, you use the _____; to
determine if they are the same object, you use the _____.
Answer: .equals() method; == operator
3. I am a method with three arguments. The first part displays an XML layout, the
second part applies the layout parameters to the container, and the third part is false,
a Boolean type declaring that that layout was already passed to the container. Who
am I?
Answer: inflate() method

Self-Assessment
1. You now have experience creating an app using an empty Activity and using a
template with placeholder content. Which of these methods do you find more
enjoyable overall? What aspects of each did you find most and least
ergonomic?
2. Which method do you expect to employ more often as a professional
developer? For which type of app projects do you anticipate using each route?

Summary
Chapter objectives

411
Android Bootcamp
for Developers
Using Java, 4e
Chapter 10: Move! Creating
Animation

• 10.01 Create an Android application with Frame and Tween animation
• 10.02 Create frame-by-frame animation
• 10.03 Set the background resource
• 10.04 Use the start() and stop() methods
• 10.05 Move with Tween animation

• 10.06 Launch Tween animation
• 10.07 Add the layout for the Tween image
• 10.08 Set Tween animation attributes
• 10.09 Code the startAnimation() method
• 10.10 Change the orientation of the emulator

10.1 Creating an Android Application with
Frame and Tween Animation (1 of 11)
• Animation is everywhere
− For example, in Dragon Ball Legends, Baldur's Gate, Word Link, Minecraft,
and Candy Crush
• A motion tween is used to animate an object and specifies
− A start state
− A uniform transition type
− The number of times to repeat the motion

Figure 10-1 Northern Lights
Animation app using Frame
animation
Figure 10-2 Northern Lights
Animation app using Tween
animation

• Steps to create the Northern Lights Animation app:
1. Add the layout for the image and button objects in activity_main.xml.
2. Add five images to the drawable folder.
3. Add a Frame animation XML file to the project.
4. Set the duration between frames in the frame-by-frame animation.
5. Declare and instantiate the ImageView, Button, and animationDrawable
controls.

• Steps to create the Northern Lights Animation app (continued):
6. Code the OnClickListeners for the Button controls.
7. Run the Frame animation application.
8. Add a Tween animation XML file to rotate the last image.
9. Create a second Activity named Tween.java to launch the rotation Tween
animation with an XML layout.
10.When the application executes, change the orientation of the emulator.

• Using Animation in Android
− Android provides two types of animation: Frame and Tween
− Frame animation (a.k.a. frame-by-frame animation) assigns a sequence of photos
to play with a predefined interval between images
 Like a slide show
 Images rapidly replaced by new, similar images
− Tween animation is created by a series of transformations on a single image
 Transformations can alter position, size, rotation, and transparency

• Adding the Layout for the Frame Image and Button Controls
− The layout specifications reside in a ConstraintLayout in activity_main.xml
− An ImageView control (ivLights) displays the Frame animation
− Two button controls (btStart and btStop) start and stop the animation,
respectively
− A Tween animation (a second Activity) is launched when the Frame
animation ends
− The "Help me choose" link can be referenced when selecting the minimum
SDK for a project

project in the New Project
window

Figure 10-4 String table

Figure 10-5 ImageView XML
code

Figure 10-6 Two Button
controls in the XML code
(Part 1)

Figure 10-6 Two Button
controls in the XML code
(Part 2)

10.2 Creating Frame-by-Frame Animation
(1 of 7)
• An animation-list root element is needed to reference images stored in the
drawable folders
− Each item in the animation-list code specifies how many milliseconds to
display the image
• The opening animation-list tag includes the android:oneshot attribute
− Set to true by default: the animation plays once and then stops and displays
the last frame
− When it is set to false, the animation plays repeatedly

(2 of 7)
• Code syntax for the animation-list element:
<animation-list
xmlns:android="http://schemas.android.com/apk/res/android"
android:oneshot="false" >
<item android:drawable="@drawable/lights1" android:duration= "100"/>
</animation-list>

(3 of 7)
• To create a Frame animation XML file, you:
− Add the image files to the drawable resources folder
− Add an XML file of the Animator resource type with animation-list as the root
element
− Nest an item element for each frame of the animation (image) within the
animation-list element

(4 of 7)
Figure 10-8 Creating the
animation.xml file

(5 of 7)
Figure 10-10
Entering the
animation-list
items with image
names and
duration

(6 of 7)
• Coding the AnimationDrawable Object
− The AnimationDrawable class provides the methods for drawable
animations to create a sequence of frame-by-frame images played in order
− In Android development, frame-based animations and image transitions are
defined as drawables
− The instance of AnimationDrawable is instantiated as a class variable
because it is used in multiple methods within the MainActivity class

(7 of 7)
Figure 10-11
Instantiating the
AnimationDrawable
class variable

10.3 Setting the Background Resource
(1 of 6)
• The Background property of an image can be set to any full drawable resource, such
as a .png file, a 9-patch image file, or a solid color
• A 9-patch image has predefined “stretching” areas that maintain the same look on
different screen sizes
− Named for the nine areas, called patches, that scale separately
• The setBackgroundResource() method places images in a frame-by-frame display
that resembles a slide show
− Each frame points to one of the images that were assembled in the XML resource
file
− The ImageView instance is the image that you want to animate; the image is set to
the animation drawable as its background

(2 of 6)
• Syntax for setting the background resource:
ImageView ivFrame=findViewById(R.id.ivLights);
ivFrame.setBackgroundResource(R.drawable.animation);
lightsAnimation=(AnimationDrawable)
ivFrame.getBackground();
− The first line instantiates the ImageView control
− The second line sets the animation-list code within animation.xml as the
Background property of the ivFrame ImageView
− The third line assigns the instance of AnimationDrawable called
lightsAnimation as the background of the five images to display in the
animation

(3 of 6)
Figure 10-14 The
getBackground() method
prepares the
AnimationDrawable object

(4 of 6)
• Adding Two Button Controls
− The Button controls in the Northern Lights Animation app turn the Frame
animation on and off
− Both use a setOnClickListener to await user interaction
− For the app project, you must write code to instantiate each Button control
and then to add the setOnClickListener to each

(5 of 6)
Figure 10-16 Coding the
button to start the Tween
animation

(6 of 6)
Figure 10-18 OnClickListener
for the second button

1. How does Tween animation work?
2. What is an animation-list?
3. What kind of image has predefined “stretching” areas that maintain the same
look on different screen sizes?

1. How does Tween animation work?
Answer: Tween animation creates animation by performing a series of
transformations on a single image such as changing its position, size, rotation,
and transparency.
2. What is an animation-list?
Answer: An element used to list, in sequence, the images that will be
displayed in an animation.
3. What kind of image has predefined “stretching” areas that maintain the same
look on different screen sizes?
Answer: 9-patch image

10.4 Using the start() and stop() Methods
(1 of 2)
• After associating AnimationDrawable with the animation images and coding the
buttons, you can use the start() and stop() methods of the drawable objects to
control the Frame animation
− Syntax:
lightsAnimation.start();
lightsAnimation.stop();
• The start() method begins the Frame animation to run continuously because
oneshot is set to false
• The stop() method thus must be called to stop the animation when the button
that begins the Tween animation for the app is tapped

10.4 Using the start() and stop() Methods
(2 of 2)
Figure 10-20 Entering the
stop() method

10.5 Moving with Tween Animation
• Tween effects are transitions that change objects from one state to another
− Alpha: transitions an object from one level of transparency to another, where
0.0 is transparent and 1.0 is opaque
− Rotate: spins an object from one angular position to another
− Scale: transitions the size of an object (grow or shrink) on an X/Y scale
− Translate: moves the object vertically or horizontally by a percentage relative
to the element width

10.6 Launching Tween Animation (1 of 3)
• The "Start Tween Animation" button in the Northern Lights Animation app
triggers two actions within the second onClick() method
− The stop() method concludes the Frame animation
− A startActivity intent launches a second Activity named Tween.java
• A new Java class and a second XML layout file must be created for the new
Activity

Figure 10-22 Creating the
Tween.java class and
activity_tween layout

Figure 10-23 The startActivity
launches the Tween class

10.7 Adding the Layout for the Tween Image
(1 of 2)
• The second Activity, Tween.java, defines a second layout named
activity_tween.xml
• This XML layout contains a single ImageView control called ivTween
− It references the fifth image named lights5 that will be rotated with the Tween
animation

10.7 Adding the Layout for the Tween Image
(2 of 2)
control coded in
activity_tween.xml

10.8 Setting Tween Animation Attributes
(1 of 4)
• Android uses an XML file-creator utility that supports 10 different resource types
that can be set as attributes
− The default type is Layout
− The Tween animation resource type can be used to create an XML file for a
Tween animation
− You use this type with rotate as the root element to code a rotation
• Attributes set within the rotate element's opening tag are used to define the
Tween animation

(2 of 4)
• Rotation attributes:
− android:fromDegrees="0" and android:toDegrees="359" spin the
object from 0 to 359 degrees (360 degrees total)
− android:pivotX="50%" and android:pivotY="50%" set the pivot
point for the rotation at the center of the object
− android:duration="2000" sets the duration for each rotation to 2,000
milliseconds
− android:repeatCount="5" will rotate the object six times (it sets the
number of rotations after the initial rotation)

(3 of 4)
Figure 10-25 New Resource
File dialog box

(4 of 4)
Figure 10-26 The rotate
attributes in rotation.xml
within the anim folder

10.9 Coding the startAnimation() Method
(1 of 2)
• The StartAnimation() method begins animating a View object by calling the
AnimationUtils class utilities to access the resources necessary to load the
animation
• A Tween animation can perform a series of simple transformations with
startAnimation(), changing position, size, rotation, and/or transparency on the
contents of a View object

10.9 Coding the startAnimation() Method
(2 of 2)
Figure 10-28 Image rotates
using Tween animation
(completed code for
Tween.java)

1. Which tween effect makes an object appear to grow or shrink?
2. What files were added to the Northern Lights Animation app to create the
image rotation effect?
3. Which rotate attribute or attributes are used to set the point around which the
object rotates?
4. How can you apply a Tween animation to a View object in order to launch the
tween effect?

(1 of 2)
1. Which tween effect makes an object appear to grow or shrink?
Answer: scale
2. What files were added to the Northern Lights Animation app to create the
image rotation effect?
Answer: Tween.java and activity_tween.xml
3. Which rotate attribute or attributes are used to set the point around which the
object rotates?
Answer: pivotX and pivotY

(2 of 2)
4. How can you apply a Tween animation to a View object in order to launch the
tween effect?
Answer: Call the startAnimation() method on the View object

10.10 Changing the Emulator to Landscape
Orientation
• The default screen orientation layout for the emulator is vertical
• Shortcuts for switching to a landscape orientation:
− On a PC: Fn + left Ctrl + F12 or 7 on the keypad with Num Lock off
− On a Mac: Fn + Ctrl + F12
− Click the Run app button
− Test the two buttons' functionality
− Practice changing the orientation of the emulator

Self-Assessment
1. What is your favorite app that features animations prominently? How are they
utilized in this app, and how do they contribute to your experience as a user?
2. Think about the categories of apps you would like to develop as a
professional. To what extent, and in what capacity, would they incorporate
animations? Which of the two types of Android animations you learned about
in Chapter 10 do you expect these effects would be coded as?

Summary
Chapter objectives

460
Android Bootcamp
for Developers
Using Java, 4e
Chapter 11: Discover! Persistent
Data

Chapter Objectives
• 11.01 Create an Android project using persistent data
• 11.02 Use different types of shared preferences
• 11.03 Use internal and external storage
• 11.04 Save to a database connection
• 11.05 Save data using a network connection
• 11.06 Write persistent data using a SharedPreferences object
• 11.07 Retrieve data using the getString() method

Persistent Data (1 of 4)
Figure 11-1 Electric Car
Financing app
Figure 11-2 Car payment
computed using persistent
data in second Activity

• Steps required to create the Electric Car Financing app:
1. Add strings to the String table.
2. Add images to the drawable folder.
3. Design two XML layouts for the first and second Activity.
4. Instantiate the XML components in the first Activity.
5. Establish a SharedPreferences object to store the data entered.
6. Write data to the SharedPreferences object.

• Steps required to create the Electric Car Financing app (continued):
7. Launch a second Activity.
8. Initialize the XML components on the second Activity.
9. Retrieve the data from the SharedPreferences object.
10.Calculate the monthly payment for the car loan and display the appropriate
image for the number of loan years using an If structure.
11.Display the monthly payment on the second Activity.

• Persistent data stores values permanently by placing the information in a file
• Persistent data can be stored in five ways in Android applications:
− Shared preferences, which stores private data in key-value pairs
− Internal storage, which stores private data in the memory of the device
− External storage, which stores data that can be available to other apps on shared
external storage
− SQLite database, which stores structured data in a private database
− Network connection, which stores data on a web server

11.2 Using Different Types of Shared
Preferences
• The SharedPreferences object can be used to save any primitive data: Booleans,
floats, ints, longs, and strings
• Shared preferences are best when your app needs to save small chunks of data in a
name/value pair
• Steps necessary to save persistent data in a SharedPreferences file:
− Obtain an instance of the SharedPreferences file
− Create a SharedPreferences.Editor object
− Assign values to SharedPreferences objects using the putString() method
− Save the values to the preferences file using the commit() method

11.3 Using Internal and External Storage
(1 of 2)
• Internal storage means storing the information directly on the device’s internal
drive
− Saved files on the device are available only to the app that created the files
− Be careful: insufficient internal storage space can drastically affect the speed
of an Android device and its battery life

11.3 Using Internal and External Storage
(2 of 2)
• Android apps can save persistent data to external storage, e.g., the device’s SD
(Secure Digital) card
• All applications can read and write files placed on the external storage and the
Android smartphone or tablet owner can remove them
• To use external storage, the following permissions are necessary in the Android
Manifest file:
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission
android:name="android.permission.READ_EXTERNAL_STORAGE"/>

11.4 Saving to a Database Connection
• A database is the perfect choice for storing a large amount of data
• SQLite is a lightweight, preloaded mobile database engine
• SQLite has been available since the Cupcake 1.5 version of Android
• It occupies a small amount of disk memory
• Android apps model data items in tables and columns, with optional
relationships between the entities within the database
• The tables can be queried using SQL statements (SQL stands for Structured
Query Language)

1. What are the five ways to store persistent data in an Android application?
2. What step must you take before you can use external storage to save Android
app data?

1. What are the five ways to store persistent data in an Android application?
Answer: SharedPreferences object (stores private data in key-value pairs)
Internal storage (stores private data in the memory of the device)
External storage (stores data that can be available to other apps on shared external
storage)
SQLite database (stores structured data in a private database)
Network connection (stores data on a web server)
2. What step must you take before you can use external storage to save Android app
data?
Answer: Add the WRITE_EXTERNAL_STORAGE and
READ_EXTERNAL_STORAGE permissions to the Android Manifest file.

11.5 Saving Data Using a Network
Connection (1 of 20)
• If connected to the Internet (a 4G/5G or Wi-Fi connection), persistent data can
be stored and retrieved using a web service
• Before an app attempts to connect to a network, it should check to see whether
an Internet connection is available
• If a connection is not available, the user cannot save or retrieve the persistent
data

• Creating XML Layout Files
− First, create the Electric Car Financing project with API 23: Android 6.0
(Marshmallow) as the minimum SDK
− Load the images into the drawable folder
− Enter the strings for display into the String table
− Drag into and position components within the emulator: a TextView, three
EditText Number components, a Button, and an ImageView
− Modify the XML code to customize the components

Electric Car Financing project

Figure 11-4 Image files in the
drawable folder

Figure 11-5 String values for
the app

<EditText
android:id="@+id/tvYears"
android:layout_below="@+id/tvTitle"
android:ems="10"
android:hint="@string/hint1"
android:inputType="number"
app:layout_constraintBottom_toBottomOf="parent"

<EditText
android:id="@+id/tvLoan"
android:layout_below="@+id/tvYears"
android:ems="10"
android:inputType="number"
app:layout_constraintBottom_toBottomOf="@+id/ivOpening"

<EditText
android:id="@+id/tvInterest"
android:layout_below="@+id/tvLoan"
android:ems="10"
android:inputType="numberDecimal"

• Creating a Second Activity and XML Layout
− Create a second Activity, which consists of a second class and a second
XML layout file
− Drag into and position within the emulator the UI components: two TextView
components and one ImageView component
− Modify the layout XML code to customize the components

Figure 11-7 Creating a second
class named Payment and a
second XML layout named
activity_payment

<TextView
android:id="@+id/tvTitle2"

<TextView
android:id="@+id/tvMonthlyPayment"
android:layout_below="@+id/tvTitle2"

• Instantiating the XML Components
− Instantiate the EditText components from the first Activity
− Instantiate the Button component from the first Activity, creating an
− Initialize the variables that will be used for calculations to values parsed from
the user's entries in the EditText components

Figure 11-9 EditText
components instantiated

Figure 11-10 Button

Figure 11-11 Variables
intYears, intLoan, and
decInterest assigned

11.6 Writing Persistent Data with
SharedPreferences (1 of 5)
• Data is saved to an XML file as a key-value pair
− The key is a string such as “key1” that uniquely identifies the preference
− The value is the data represented as a string, int, long, float, or Boolean
• Data types supported by the SharedPreferences class:
− putString()—stores string values
− putInt()—stores integer values
− putLong()—stores long values
− putFloat()—stores float values
− putBoolean()—stores Boolean values

• Java syntax for storing data with the SharedPreferences object:
final SharedPreferences sharedPref =
PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putInt("key1", intYears);
editor.putInt("key2", intLoan);
editor.putFloat("key3", decInterest);
editor.commit();
• Within the editor, you can also remove a single preference pair using the
remove() method or remove all preferences using the clear() method

Figure 11-13 Three values
(persistent data) written in an
XML data file

• Launching the Second Activity
− Add the statement startActivity(new
Intent(MainActivity.this, Payment.class)); to the onClick()
method
• Instantiating the Second Activity Components
− Instantiate the TextView and ImageView components

Figure 11-15 Instantiating the
TextView and ImageView
components in Payment.java

11.7 Retrieving Data Using getString()
Methods (1 of 7)
• You do not need an editor to read saved data in SharedPreferences
• Retrieve the SharedPreferences object and use the appropriate method to
retrieve a key’s value by name
− getString()—retrieves string values
− getInt()—retrieves integer values
− getLong()—retrieves long values
− getFloat()—retrieves float values
− getBoolean()—retrieves Boolean values

Methods (2 of 7)
• Each "get" method has two parameters: the preference key string and a default
value to return if the preference is undefined
• Java syntax for creating a SharedPreferences instance and loading data from
the persistent data XML file:
SharedPreferences sharedPref =
PreferenceManager.getDefaultSharedPreferences(this);
int intYears = sharedPref.getInt("key1", 0);
int intLoan = sharedPref.getInt("key2", 0);
float decInterest = sharedPref.getFloat("key3", 0);

Methods (3 of 7)
Figure 11-17
SharedPreferences values are
retrieved

Methods (4 of 7)
• Displaying the Correct ImageView Component
− An ImageView control can display an image by assigning a source path
(android:src="drawable/filename") in the XML layout file
− Alternatively, it can display an image by dynamically assigning the image
within the Java code:
image.setImageResource(R.drawable.three);
− For the Electric Car Financing app, a monthly payment is calculated and
formatted for display
− A nested If decision structure is used to select an image to display

Methods (5 of 7)
Figure 11-19 The monthly
payment is displayed in the
second Activity

Methods (6 of 7)
Figure 11-21 Closing Else
statement

Methods (7 of 7)
− Run the app in the emulator
− The first Activity saves data you enter to an XML file using the
SharedPreferences object
− The second Activity launches the Payment.java file, which retrieves the
stored data and calculates the monthly payment for the car loan
− The monthly payment is shown, and a decision structure determines which
image should be displayed to indicate the loan term

1. What is the difference between a key and a value in a SharedPreferences
XML file?
2. What two SharedPreferences class methods would you call to store an integer
value?
3. What methods of the SharedPreferences object are used to retrieve Android
data?
4. What Java method can you use to dynamically assign an image to display
within an ImageView component?
5. Answer: setImageResource()

(1 of 2)
1. What is the difference between a key and a value in a SharedPreferences
XML file?
Answer: The key is a string such as “key1” that uniquely identifies the
preference, and the value is the data represented as a string, int, long, float, or
Boolean value.
2. What two SharedPreferences class methods would you call to store an integer
value?
Answer: putInt() and commit()

(2 of 2)
3. What methods of the SharedPreferences object are used to retrieve Android
data?
Answer: getString() retrieves string values
getInt() retrieves integer values
getLong() retrieves long values
getFloat() retrieves float values
getBoolean() retrieves Boolean values
4. What Java method can you use to dynamically assign an image to display
within an ImageView component?
Answer: setImageResource()

Self-Assessment
1. Think about the kinds of Android applications you anticipate working on as a
developer. What kinds of data, and what quantities of data, would these apps
need to store and retrieve to function usefully?
2. Which of the methods for storing persistent data that you learned about in
Chapter 11 do you think should be used for the apps you envisioned?
3. Consider the personal data that many apps store about individuals. How much
do you know about the coding practices and other procedures used to
safeguard personal data? What else do you need to learn to write apps that
offer reasonable data protection?

Summary
Chapter objectives

509
Android Bootcamp
for Developers
Using Java, 4e
Chapter 12: Finale! Publishing
Your Android App

Chapter Objectives
• 12.01 Describe Google Play
• 12.02 Target various device configurations and languages
• 12.03 Test your app before publishing
• 12.04 Create an Android App Bundle
• 12.05 Prepare promotional materials to upload to Google Play
• 12.06 Publish your app on Google Play

12.1 Using Google Play (1 of 3)
• There are many distribution networks
• Apps can be published to:
− Google Play (Google’s app store, the largest marketplace)
− Amazon Appstore
− Huawei AppGallery
− Xiaomi Mi GetApps
− Aurora

• Steps to publish an app:
1. Test the app
2. Prepare the app for publication
3. Create an AAB package and digitally sign the application
4. Prepare promotional materials
5. Publish the app to Google Play

• Google Play is a digital repository that serves as the online storefront for paid
and free Android apps
− URL: https://play.google.com
− Contains the features and services of Android apps, Google Music, and
Google e-books
− Provides free cloud storage services
− Used by over 190 countries
− Apps selected on Google Play install directly to the Android device
− Part of the default setup on new Android devices

12.2 Targeting Device Configurations and
Languages (1 of 4)
• You can reach a larger audience by translating your app into multiple languages
• To support multiple languages:
− Create a resource directory for each language in the strings directory (the
strings.xml file) using the Translations Editor
− One application then recognizes multiple languages
• You can use the Google Translate service (https://translate.google.com) to
translate into over 100 different languages

Languages (2 of 4)
• Adding Localization Using the Translations Editor
− The Android Studio Translations Editor supports multiple languages
− Localization: the process of adapting an app or web page to a language
while considering cultural differences
 Differences include whether the language is read left-to-right or right-to-
left, calendar layout, measurements, currency, date and time formats,
and traditions of the target audience
− The globe-shaped Add Locale icon in the Translations Editor provides
access to a list of locales around the world

Languages (3 of 4)
Figure 12-2 Locale listing in
the Translations Editor

Languages (4 of 4)
Figure 12-4 Red text
on key designates
missing translation

12.3 Testing Your App before Publication
• Use the Android Studio built-in emulators to test an app's design and
functionality
• Check real-world functionality by using the Android Debug Bridge (ADB),
which allows Android Studio to communicate with a connected Android device
− Access the Settings > Developer options on the device and check the USB
debugging option
− Install a USB driver for ADB on the computer (Windows only)
− Run the app in Studio and select the connected device

12.4 Creating an Android App Bundle (1 of 5)
• The required app package format for Google Play is Android App Bundle
(AAB) format
• An .aab file is similar to a .zip file that contains the application, the manifest file,
and all associated resources, such as image files, music, and other required
content
• You use the Android Studio Build menu to build a release-ready .aab file signed
with your private key and optimized for publication
− All Android apps must be digitally signed with a certificate that identifies the
author and establishes trust relationships between applications

Figure 12-6 Using the Build
menu in Android Studio

Figure 12-7 Generate Signed
Bundle or APK dialog box

Figure 12-8 Creating a key in
the Generate Signed Bundle
or APK dialog box

Figure 12-9 Selecting the
debug option

1. Which tool is used to communicate with a connected Android device through Android
Studio?
2. When you adapt an app or web page to a language while considering cultural
differences such as the direction in which the language is read, date and time
formats, units of measurement, and currency, you are adding _____.
3. To publish an app on Google Play, you must package it in _____ format, which has
the _____ file extension.
4. What is used to sign your Android application with information from your local
system?

1. Which tool is used to communicate with a connected Android device through Android Studio?
Answer: Android Debug Bridge (ADB)
2. When you adapt an app or web page to a language while considering cultural differences such
as the direction in which the language is read, date and time formats, units of measurement,
and currency, you are adding _____.
Answer: localization
3. To publish an app on Google Play, you must package it in _____ format, which has the _____
file extension.
Answer: Android App Bundle (AAB), .aab
4. What is used to sign your Android application with information from your local system?
Answer: A private key or certificate

12.5 Preparing Promotional Materials to
Upload (1 of 11)
Figure 12-10 National
Geographic Android app from
Google Play

Upload (2 of 11)
• Providing Images
− Application icon (required): 512 x 512 pixels in size, stored in a 32-bit .png
file
− Screenshots (2 required; up to 8): 480 x 320, 800 x 480, or 854 x 480 pixels
in size; PNG files
− Video that demonstrates the app (optional): should highlight the top features
and be between 30 seconds and 2 minutes
 Can link to the video on YouTube

Upload (3 of 11)
• Providing a Description
− An app description provides a quick overview to the purpose of the app and
what it does
− Include features the app provides
− You want to sell the app to the widest audience possible
− Motivate users to download the app
− Revise the description as you update the app
− Utilize quotes from positive reviews when possible

Upload (4 of 11)
Figure 12-12 National
Geographic reviews

Upload (5 of 11)
• Providing a Description (continued)
− Pricing an app
 Users may try a free app, then buy additional features, including in-app
purchases
 Some users will never pay for an average app, but many will pay for a
great one
− When you upload an app to Google Play, you select one or more of the
application categories to classify it

Upload (6 of 11)
Category Example Types of Apps
Books & Reference Book readers, reference books, textbooks, dictionaries, thesauruses, wikis
Business Document editors/readers, package tracking, remote desktops, email management, job
searches
Comics Comic players, comic titles
Communications Messaging, chat/IM, dialers, address books, browsers, call management
Education Exam preparation, study aids, vocabulary, educational games, language learning
Finance Banking, payment, ATM finders, financial news, insurance, taxes, portfolio/trading, tip
calculators
Health & Fitness Personal fitness, workout tracking, diet and nutritional tips, health and safety

Upload (7 of 11)
Libraries & Demo Software libraries
Lifestyle Recipes, style guides
Media & Video Subscription movie services, remote controls, media/video players
Medical Drug and clinical references, calculators, handbooks for healthcare providers, medical
journals and news
Music & Audio Music services, radios, music players
News & Magazines Newspapers, news aggregators, magazines, blogging
Personalization Wallpapers, live wallpapers, home screens, lock screens, ring tones
Photography Cameras, photo-editing tools, photo management and sharing

Upload (8 of 11)
Productivity Notepads, to-do lists, keyboards, printing, calendars, backup, calculators, conversion
Shopping Online shopping, auctions, coupons, price comparison, grocery lists, product reviews
Social Social networking, check-in, blogging
Sports Sports news and commentary, score tracking, fantasy team management, game
coverage
Tools System utility tools
Travel & Local City guides, local business information, trip management tools
Weather Weather reports

Upload (9 of 11)
• Including Contact and Social Networks
− A social networking presence for your app enables you to build relationships
with customers and communicate with your fans
• Setting Versions for your App
− After an app is published, you can update it with new features and new SDK
platforms
− Allows the Android OS to check whether a newer version of the app is
available from the Google Play Store and then prompt the user to upgrade
the app, if necessary

Upload (10 of 11)
• Setting Versions for your App (continued)
− Syntax to set the version of code and version name number within the
AndroidManifest.xml file:
<manifest
xmlns:android="http://schemas.android.com/apk/res/androi
d"
xmlns:tools="http://schemas.android.com/tools"
android:versionCode="1"
android:versionName="1.0">

Upload (11 of 11)
• Registering for a Google Play Account
− A Google account is needed
− Register at https://play.google.com/apps/publish
− A one-time payment of $25 is required to register as an Android application
developer and enrolls you in a Google Merchant account
− If you charge for apps, you also obtain a Google Wallet account and Google
Merchant disperses revenue for application sales
 For the first $1 million of revenue, you get 85% and the phone carriers get 15%
 For profits >$1 million, the service fee increases to 30%

12.6 Publishing Your App to Google Play
(1 of 4)
• Once you create an account, the Developer Console pages take you through
the steps to upload your unlocked app .aab file and the promotional assets
− Maximum size for the .aab file: 150 MB
• Ensure your app complies with Google's content policies and with local laws
• After launching your app, you can visit your Dashboard page to get an overview
of the app's key metrics, trends, and insights

(2 of 4)
Figure 12-15 All apps page on
Google Play Console

(3 of 4)
Figure 12-16 Create app
website

(4 of 4)
Figure 12-17 Google Play
developers Dashboard

1. How much does it cost to register as a developer with Google Play?
2. What are the pixel dimensions of an application icon?
3. In what format should application icons be stored?
4. What is the maximum supported file size for the .aab file at Google Play?

1. How much does it cost to register as a developer with Google Play?
Answer: $25
2. What are the pixel dimensions of an application icon?
Answer: 512 x 512
3. In what format should application icons be stored?
Answer: PNG (32-bit .png file)
4. What is the maximum supported file size for the .aab file at Google Play?
Answer: 150 MB

Self-Assessment
1. Now that you have completed the lessons in this textbook, how well prepared
do you feel to write and publish your own Android apps?
2. How prepared do you feel to join a team of professional developers working
on an Android app?
3. What aspects of Android app development would you like to study further or
gain greater experience with to improve your relevant skills?

Summary
Chapter objectives

Hoisington_Android_4e_PPT_CH01.pptx

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