Ii 1300-java essentials for android

Java Essentials for Android

Presented by

Adrian Mikeliunas

Adrian@Mikeliunas.com

TASKMobileSolutions.com


MoDevAcademy

MoDevAcademy will offer professional training across
platforms that include beginner, intermediate and
advanced courses.

The format will be one day courses that can be taken
individually or paired for a multi-day experience. The
Academy intended to fill a much needed void in the
market for in-depth mobile developer training.

2

Upcoming Classes

Schedule:

• January 22nd: Starting up with iOS Development

• January 23rd: Expert Objective-C

• January 24th: Advanced Xcode Development

Register at MoDevAcademy.com/Registration

Online Resources

The references in this presentation, and many other
resources are available at:

http://Gomodev.com/MoDevAcademyResources


Agenda

 Java Similarities

 Java Differences

 Android Programming with Java in Eclipse

 Resources
 Google Samples
 F-droid.org
 SourceFourge.net

5


Android & Java Comparisons
Similarities

Differences

6


Android <> Java

 Android is Google’s Operating System, combining Linux
with their own version of Java, named Dalvik

 Dalvik uses a subset of Harmony, an Apache Software
Foundation project

 Dalvik is open-source software. Is the name of a fishing
village in Iceland

http://en.wikipedia.org/wiki/Dalvik_virtual_machine

7


Android/Java Similarities
java.io - File and stream I/O
java.lang - Language & exception
 Android uses Java syntax support
java.math - Big numbers, rounding,
precision
 Android uses similar APIs java.net - Network I/O, URLs, sockets
java.nio - File and channel I/O
java.security - Authorization, certificates,
 Android, supports a relatively public keys
java.sql - Database interfaces
large subset of the Java java.text - Formatting, natural language,
collation
Standard Edition 5.0 library …

 Java files on Android are
compiled into .class files and
then in dalvik executables(.dex)

8


Android/Java Differences

 Unlike Java VMs, which are stack machines, the Dalvik
VM uses a register-based architecture

 Dalvik does not align to Java SE nor Java ME class library
profiles

 Java is a programming language, while Android is a
mobile phone platform

9


Android/Java Differences

 Android does not use the Abstract Window Toolkit nor the
Swing library. User Interface is built using View objects

 Android layout behavior is encoded in the containers
using XML files, unlike Java where Layout managers can
be applied to any container widget

 Android relies on a master AndroidManifest.xml file
 There is no Main class
 You need to define default activity here
 THIS IS A MANUAL METHOD

10


Android & Eclipse
Setup

Components

Development

11


Android Development Setup - 1

 Your Development Computer
 Install Java Development Kit (JDK)
 www.oracle.com/technetwork/Java/javase/
downloads/index.html
 Install Eclipse Classic version
 www.eclipse.org/downloads

 Requirements:
 Windows, Mac, or Linux
developer.android.com/sdk/requirements.html

12

JDK

www.oracle.com/technetwork/Java/javase/
downloads/index.html

13

Eclipse

www.eclipse.org/downloads

14

Android Development Setup - 2
 Downloading the SDK Starter Package
 Install Android SDK
http://developer.android.com/sdk/index.html

15

Android SDK Manager

16


Android Development Setup – 3a

 ADT Plugin for Eclipse
 Start Eclipse
 Select Help > Install New Software....
 Click Add, in the top-right corner
 In the Add Repository dialog that appears,
 enter "ADT Plugin" for the Name
 Location: https://dl-
ssl.google.com/android/eclipse/
 Click OK.

17


Android Development Setup – 3b

 ADT Plugin for Eclipse
 In the Available Software dialog, select the
checkbox next to Developer Tools and click Next.
 In the next window, you'll see a list of the tools to be
downloaded. Click Next.
 Read and accept the license agreements, then
click Finish.

 When the installation completes,
 Restart Eclipse!

18


Android Development Setup – 3c
 Select Window > Preferences...

 Select Android from the left panel
 You may see a dialog asking whether you want to send
usage statistics to Google. If so, make your choice and
click Proceed. You cannot continue with this procedure
until you click Proceed.

 For the SDK Location in the main panel, click Browse... &
locate your downloaded SDK directory

 Click Apply, then OK
http://developer.android.com/sdk/eclipse-adt.html#installing

19


Android Development Tools (ADT)
The Android SDK includes several tools &
utilities to help you create, test, & debug
your projects
ADT plug-in conveniently incorporates
most of these tools into the Eclipse IDE,
where you can access them from the
DDMS perspective

20


ADT Inventory

 The Android Emulator
 Dalvik Debug Monitoring Service
(DDMS)
 Android Asset Packaging Tool (AAPT)
 Android Debug Bridge (ADB)

21


ADT Inventory-2
The following additional tools are also
available:
 SQLite3 A database tool
 Traceview Graphical analysis tool
 MkSDCard
 dx: java bytecode to Dalvik executable
 activityCreator Script

22


Android SDK

 android.jar
 Documentation
 Samples directory
 Tools directory
 usb_driver
23

• Eclipse Navigation

• Package
Explorer
• Code Editor
• Outline View

• 2
4

• Eclipse Tools-DDMS

Dalvik
Debug
Monitor
Service

• 2
5


Android Emulator

 Create an Android Virtual Device

 Run it!

26


Android Architecture
 Applications

 Application
framework

 Libraries

 Android Runtime
(Dalvik VM)

 Linux 2.6 Kernel

27


Android Layers
 Linux kernel provides drivers for the Android hardware,
networking, file system access & inter-process-communication

 Libraries are mostly written in C or C++

 Core Libraries are the core development kit including utility,
i.o. etc

 Dalvik Virtual Machine is an optimized Java VM

 Application Framework is the API to developers

 Applications are user facing programs

29


Android Applications

• Each application runs in its own
process, gets unique identifier &
runs its own instance of Dalvik VM

 This way the processes are isolated & crash of one
application does not bring down the whole system!

30

Android Programming
 System Level – modifying the Android system
code & adapting it to various hardware platforms.
It also involves creating additional services &
features in the android system itself. C. C++

 Application level – creating software products &
services which sits on top of the Android software
stack & interacts with the hardware through the
underlying Android platform. Java.

31


Application Development Basics

 Activity
 Presents visual interface to the user
 Each activity has a separate window
 to draw the visual component but if required it can use
more than one window also

 Services
 runs in the background and carries out some
background process while the other visual component s
are running in the foreground

32


Application Development Basics-2

 Broadcast receivers
 responsible for receiving and reacting to broadcasted
messages

 Content providers
 This provides specific set of data from one application to
other applications. Used in conjunction with Content resolver
which provide methods for inter process communication

 Widgets
 These are programs anchored to the home screen
providing information updated fairly frequently

33

Android Activities
Each Android application must designate a default activity within
the Android manifest file

Android Activity Class
The Activity base class defines a series of events that governs the life cycle of an
activity:

onCreate() — Called when the activity is first created

onStart() — Called when the activity becomes visible to the user

onResume() —when the activity starts interacting with the user

onPause() —current activity is being paused & the previous activity is being resumed

onStop() —when the activity is no longer visible to the user

onDestroy() — Called before the activity is destroyed by the system
(either manually or by the system to conserve memory)

onRestart() —when the activity has been stopped & is restarting

36

Android Activity Class (2)

public void onStart()
{
super.onStart();
Log.d(tag, ―In the onStart() event‖);
}
public void onRestart()
{
super.onRestart();
Log.d(tag, ―In the onRestart() event‖);
}

37

Android Activities
 To create an activity, you create a Java class
that extends the Activity base class:
package com.example.Activities;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}

38

Android Activities-2

 Your activity class would then load its UI component
using the XML file defined in your res/layout folder. In this
example, you would load the UI from the main.xml file:
setContentView(R.layout.main);

 Every activity you have in your application must be
declared in your AndroidManifest.xml file

39

Android Activities (3)
<?xml version=‖1.0‖ encoding=‖utf-8‖?>
<manifest xmlns:android=‖http://schemas.android.com/apk/res/android‖
package=‖com.example.Activities‖
android:versionCode=‖1‖
android:versionName=‖1.0‖>
<application android:icon=‖@drawable/icon‖
android:label=‖@string/app_name‖>
<activity android:name=”.MainActivity”
android:label=‖@string/app_name‖>
<intent-filter>
<action android:name=‖android.intent.action.MAIN‖ />
<category
android:name=‖android.intent.category.LAUNCHER‖ />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion=‖9‖ />
</manifest>

40

Android Layouts

 An Android layout is a class that handles arranging
the way its children appear on the screen
 Anything that is a View (or inherits from View) can be a
child of a layout

 All of the layouts inherit from ViewGroup (which
inherits from View) so you can nest layouts
 You could also create your own custom layout by making a
class that inherits from ViewGroup

41

The Android Layouts are:

AbsoluteLayout
FrameLayout
LinearLayout
RelativeLayout
TableLayout
42


Android Resources

 Google Samples

 F-droid.org

 sourceforge.net

43


Example: Timesheet

 Timesheet is an application designed primarily for contractors
and freelancers to track the time spent on different tasks.
http://tastycactus.com/projects/timesheet/
f-droid.org/repository/browse/?fdfilter=timesheet&fdid=com.tastycactus.timesheet
play.google.com/store/apps/details?id=com.tastycactus.timesheet

44



Q& A

45

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