1. Android Application
-Architecture

2. Course Objectives Platform architecture Application building blocks
Application Lifecycle
Android security model

3. Introduction to Android
Open software platform for mobile development
A complete stack – OS, Middleware, Applications
An Open Handset Alliance (OHA) project
Powered by Linux operating system
Fast application development in Java
Open source under the Apache 2 license

4. Android architecture

5. Linux Kernel Works as a HAL Device drivers Memory management
Process management
Networking

6. Libraries C/C++ libraries Interface through Java
Surface manager – Handling UI Windows
2D and 3D graphics
Media codecs, SQLite, Browser engine

7. Android Runtime Dalvik VM Core Libraries Dex files
Compact and efficient than class files
Limited memory and battery power
Core Libraries
Java 5 Std edition
Collections, I/O etc…

8. Application Framework
API interface
Activity manager – manages application life cycle.

9. Applications
Built in and user apps
Can replace built in apps

10. Course Objectives Platform architecture Application building blocks
Application Lifecycle
Android security model

11. Application Building Blocks
Activity
IntentReceiver
Service
ContentProvider

12. Activities Typically correspond to one UI screen But, they can:
Be faceless
Be in a floating window
Return a value

13. IntentReceivers Components that respond to broadcast ‘Intents’
Way to respond to external notification or alarms
Apps can invent and broadcast their own Intent

14. Intents
Think of Intents as a verb and object; a description of what you want done
E.g. VIEW, CALL, PLAY etc..
System matches Intent with Activity that can best provide the service
Activities and IntentReceivers describe what Intents they can service

15. Intents System picks best component for that action
Home
Photo Gallery
Contacts
“Pick photo”
GMail
Client component makes a request for a specific action
Chat
Blogger
Blogger
New components can use existing functionality

16. Services Faceless components that run in the background
E.g. music player, network download etc…

17. ContentProviders Enables sharing of data across applications
E.g. address book, photo gallery
Provides uniform APIs for:
querying
delete, update and insert.
Content is represented by URI and MIME type

18. Notification Manager How background app interact with users
Consistent notification presentation

19. Notification Manager

20. Course Objectives Platform architecture Application building blocks
Application Lifecycle
Android security model

21. Application Lifecycle
Application run in their own processes (VM, PID)
Processes are started and stopped as needed to run an application's components
Processes may be killed to reclaim resources

22. Lifecycles Notifications
As an activity transitions from state to state, it is notified of the change by calls to the following protected methods:
void onCreate(Bundle savedInstanceState) void onStart() void onRestart() void onResume() void onPause() void onStop() void onDestroy()

23. Lifecycles Notifications
All of these methods are hooks that you can override to do appropriate work when the state changes.
All activities must implement onCreate() to do the initial setup when the object is first instantiated.
Many will also implement onPause() to commit data changes and otherwise prepare to stop interacting with the user.

25. Course Objectives Platform architecture Application building blocks
Application Lifecycle
Android security model

26. Android Security Model
Permission-based Security Model

27. Android Security Model
Android is a privilege-separated operating system, in which each application runs with a distinct system identity(Linux user ID and group ID)

28. Android Security Model
User Permissions in the AndroidManifest.xml
• INTERNET: Access the Internet.
• READ_CONTACTS: Read (but don’t write) the user’s contacts data.
• RECEIVE_SMS: Monitor incoming SMS (text) messages.
• ACCESS_COARSE_LOCATION: Use a coarse location provider such as cell towers or Wi-Fi.
• ACCESS_FINE_LOCATION: Use a more accurate location provider such as GPS.
For example, to monitor incoming SMS messages you’d specify this in the manifest file:
<manifest xmlns:android="
package="com.google.android.app.myapp" >
<uses-permission android:name="android.permission.RECEIVE_SMS" />
</manifest>