1. Android Middleware Bo Pang Bpang@cc.hut.fi

2. Android System Architecture Source: Google

3. overview • Linux Kernel: memory management, process management, networking, and other operating system services. • Native Libraries: written in C or C++, including: Surface Manager, 2D and 3D graphics, Media codes, SQL database, Browser engine, etc. only to be called by higher level programs

4. overview • Android Runtime: including the Dalvik virtual machine and the core Java libraries. (not J2SE/J2ME) • Application Framework: Activity manager, Content providers, Resource manager, Notification manager • Applications and Widgets: the real programs display information and interact with users.

5. Media Framework • Android use OpenCore as core component of Media framework • OpenCore supports MP3, AAC, AAC+, 3GPP, MPEG-4 and JPEG,

6. Media Framework

7. Media Framework • Example: •   MediaPlayer mp = new MediaPlayer(); •   mp.setDataSource(PATH_TO_FILE); •    mp.prepare(); •    mp.start();

8. Media Framework • OpenCore lib has a C/S Architecture. • MediaPlayer invoke JNI to manipulate client. • The client request to the server to control hardwares.

9. Media Framework

10. Media Framework

11. Activity Manager • each user interface screen is represented by an Activity class. • Each activity has its own life cycle. • Activity uses Intent object to jump between them.

12. Life cycle of activity Source: Hello Adroid

13. Intent and Intent filters • Intent activates activities, services, and broadcast receivers. • Intent can be used in explicit way or implicit way. • The implicit way depends on parameters: Action, Data(url and MIME type) , Category

14. Intent and Intent filters • To receive other components' request, components’ need to register filters at activities framework. • When launch a intent object, framework will match and find the qualified components and leave them for users to choose which to run.

15. Intent and Intent filters • Example • <intent-filter>                <action android:name="android.intent.action.VIEW" />                <action android:name="android.intent.action.EDIT" />                <action android:name="android.intent.action.PICK" />                <category android:name="android.intent.category.DEFAULT" />                <data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />            </intent-filter>

16. Activities and Tasks • A task is a stack which contain several activities share the same affinity. Source: http://blog.akquinet.de/2010/02/17/android-activities-the-predominance-of-the-ui-thread/

17. Activities and Tasks • There are four different launch modes that can be assigned to an <activity> element's launchMode attribute: • "standard" (the default mode) "singleTop" "singleTask" "singleInstance" • First two share the same affinity with application, the others don’t.

18. Content manager • Manage data • Client+server architecture. • Content Resolver provides API interface for applications. • Content Providers is the server managing the DB tables and database content with different application.

19. Content manager Source: Google • URI identifies the data or the table • A: Standard prefix indicating that the data is controlled by a content provider. • B: The authority part of the URI; it identifies the content provider. • C: The path that the content provider uses to determine what kind of data is being requested. • D: The ID of the specific record being requested.

20. Service Lifecycle

21. Security and permissions • security between applications and the system is enforced at the process level through standard Linux facilities • Application can't disrupt other applications, except by explicitly declaring the permissions it • Each Android package is given its own unique Linux user ID

22. References • http://www.j2medev.com/android/ShowArticle.asp?ArticleID=5439 • http://docs.huihoo.com/google/io/2009/Mastering_the_Android_Media_Framework.pdf • http://developer.android.com/