This document discusses key concepts for mobile application development on Android including activities, layouts, menus, dialogs, intents, notifications, and services. It describes how to create an activity by extending the Activity class and setting the user interface. It also explains the different types of layouts, menus, and dialogs available in Android and how to implement them.

1. Mobile Application Development
Activity & Services

2. Android User Interfaces
1. Activities
2. Layouts
3. Menus
4. Dialogs
5. Intents
6. Notifications

3. Creating an Activity
• Create a new Activity by extending the Activity class.
• Override the onCreate() method to set the view for the
activity
• Set the user interface to an Activity using the
setContentView() method in the onCreate method of
the Activity.
public class MyActivity extends Activity {
public void onCreate(Bundle b) {
super.onCreate(b);
setContentView(R.layout.main);
}
}

4. • Activities in the system are managed as an activity stack.
• The Android memory manager uses this stack to determine
the priority of applications based on their Activities when
deciding which application to terminate to free resources.
• An activity has essentially four states:
 Active : An activity in the foreground of the screen.
 Paused : An activity has lost focus but is still visible.
 Stopped : An activity is completely obscured by another
activity.
 Inactive : After an Activity has been killed or before it has
been launched.
Activity Life Cycle

6. Activity Lifetimes
• Entire lifetime :
Happens between the first call to onCreate(Bundle) through
to a single final call to onDestroy(). An activity will do all
setup of "global" state in onCreate(), and release all remaining
resources in onDestroy().
• Visible lifetime :
Happens between a call to onStart() until a corresponding call
to onStop(). During this time the user can see the activity on-
screen, though it may not be in the foreground and
interacting with the user.
• Foreground lifetime :
Happens between a call to onResume() until a corresponding
call to onPause().

7. Layouts
• Layout is the design plan or the architecture for the
user interface in an activity.
• Layout is required to arrange or organize the widgets
inside an activity.
• Layout defines the activity structure & holds all the
elements that are part of the user interface.
• Layouts can be nested.

8. A Layout can be declared in two ways:
• Declaring in XML:
Android provides a straightforward XML tags that
corresponds to the View classes and subclasses, such as
those for widgets and layouts that can be added to the
layout.
• Instantiating at runtime:
Your application can create View and ViewGroup objects
(and manipulate their properties) programmatically.
Declaring Layout

9. • Linear Layout
A layout that organizes its children into a single horizontal or
vertical row.
• Table Layout
A layout that positions its children into rows and columns.
• Relative Layout
A layout that allows to organize child elements in positions
relative to the parent or siblings elements.
• Frame Layout
It is designed to block out an area on the screen to display a
single item.
Layout Types

11. Menus
• Menus provide familiar interfaces to expose
application functions without sacrificing screen
space.
• Android offers an easy programming interface to
provide standardized application menus.
• Android offers three fundamental types of
application menus:
 Options Menu
 Context Menu
 Sub-menu

12. • By default, every Activity supports an Options menu. It
is revealed by pressing the device MENU key.
• Options Menu has two groups of menu items:
Icon Menu
 Collection of maximum of six menu items
 Supports Icons and short-cuts
Expanded Menu
 Exposed by the 'More' menu item
 Displayed when the icon menu becomes over-loaded
 Comprised of sixth options menu item and the rest.
Options Menu

13. Options Menu

14. Context Menu
• Context menu is a floating menu that is associated
with a control.
• Context menu is launched when the control has the
focus and the D pad is pressed.
• Context menus can be assigned to any View within
an Activity.
• It provides functions relating to the view, to which it
is registered.
• It supports submenus, checkboxes, radio buttons.
• It does not support shortcuts and icons.

15. Context Menu

16. • Sub menu is a floating menu, it can be a child menu of
options menu or context menu.
• It supports checkboxes, radio buttons and shortcut
keys.
• It does not support item icons, or nested sub menus.
Sub Menu

17. Sub Menu

18. • A dialog is a small window that appears in front of an
Activity.
• The underlying Activity loses focus and the dialog
accepts all user interaction.
• Normally used for notifications and short activities that
directly relate to the application in progress.
• Android supports following types of dialogs.
Alert Dialog
Progress Dialog
Date Picker Dialog
Time Picker Dialog
Toast
Dialog

19. • A dialog that can manage zero, one, two or three
buttons.
• It can also manage a list of selectable items that can
include checkboxes or radio buttons.
• The AlertDialog is capable of constructing most
dialog user interfaces and is the suggested dialog
type.
• AlertDialog class is a subclass of Dialog class and
has a nested subclass AlertDialog.Builder to
construct a dialog.
Alert Dialog

21. Other Dialogs
• Progress Dialog
A dialog that displays a progress wheel or progress
bar.
It supports buttons like in AlertDialog.
• DatePicker Dialog
A dialog that allows the user to select a date.
• TimePicker Dialog
A dialog that allows the user to select a time.

23. • A toast is a transient Dialog box containing a
quick little message for the user.
• Toasts never receive focus and they don’t
interrupt the active application.
• They provide an ideal mechanism for alerting
users to events occurring in background Services
without interrupting foreground applications.
Toast

24. • Intents are the messages that are used to activate
following application components:
Activities
Services
Broadcast Receivers
• Intent is an object, which has a data structure holding
any one of the following data :
Abstract description of an operation to be performed
In the case of broadcasts, a description of something
that has happened and is being announced.
Intents

25. Application components are invoked through intents
in the following way :
• Activity : Intent object is passed to following
functions to invoke the Activity.
Context.startActivity (Intent intent)
Activity.startActivityForResult (Intent intent, int
requestCode)
• Service : Intent object is passed to following functions
to invoke the Service.
Context.startService (Intent)
Context.bindService (Intent)
Invoking Components

26. • Broadcast Receivers : Intent object is passed to
following functions to invoke the Broadcast
Receiver.
 Context.sendBroadcast ( Intent intent, String
receiverPermission)
 Context.sendOrderedBroadcast ( Intent intent,
String receiverPermission)
 Context.sendStickyBroadcast ( Intent intent )
Invoking Components

27. • A status bar notification adds an icon to the system's
status bar (with an optional ticker-text message) and an
expanded message in the "Notifications" window.
• When the user selects the expanded message, Android
fires an Intent that is defined by the notification
(usually to launch an Activity).
• You can also configure the notification to alert the user
with a sound, a vibration, and flashing lights on the
device.
• This kind of notification is ideal when your application
is working in a background Service and needs to notify
the user about an event.
Notification

28. • To create a notification, following classes should be
used:
Notification
NotificationManager
• Notification is a class that represents how a persistent
notification is to be presented to the user using the
NotificationManager.
• NotificationManager is an Android system service used
to handle notifications.
Notification (Continued)

29. Notification (Continued)

30. Notification (Continued)

31. • A Service is an application component that runs in the
background for an indefinite period of time.
• Services are specifically used to handle operations and
functionality that should run silently, without any User
Interface.
• Services are generally used to perform following
operations in the background
 Updating the Content Providers
 Firing Intents
 Triggering Notifications etc
• Services, like other application objects, run in the main
thread of their hosting process.
Services

32. • Services are started, stopped, and controlled from
other application components including other
Services, Activities, and Broadcast Receivers.
• Service is involved in any CPU intensive (such as MP3
playback) or blocking (such as networking)
operations, should spawn its own thread to do that
work.
• Android platform has following services:
 Location Manager
 Media Controller
 Notification Manager
Services (Continued)

33. • Service supports following lifecycle methods :
 OnCreate
 OnStart
 OnBind
 OnUnbind
 OnRebind
 OnDestroy
• Service is controlled using following methods:
 Context.startService
 Context.stopService
 Service.stopSelf
 Context.bindService
 Context.UnbindService
Service Life Cycle

35. 1. Professional Android Application Development, Reto
Meier, Wrox, November 2008
2. Beginning Android, Mark Murphy, Apress, June 2009
3. Pro Android, Sayed Y Hashimi, Apress, June 2009
4. Android – Application Development, Rick Rogers et.al,
O’Reilly, May 2009
5. “Hello, Android”, Introducing Google’s Mobile
Development Platform, Ed Burnette, The Pragmatic
Bookshelf, 2008
6. developer.android.com
References