synapseindia android middleware
TRANSCRIPT
Android Middleware
Android System Architecture
Source: Google
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
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.
Media Framework
• Android use OpenCore as core component of Media framework
• OpenCore supports MP3, AAC, AAC+, 3GPP, MPEG-4 and JPEG,
Media Framework
Media Framework
• Example: • MediaPlayer mp = new MediaPlayer(); • mp.setDataSource(PATH_TO_FILE); • mp.prepare(); • mp.start();
Media Framework
• OpenCore lib has a C/S Architecture.• MediaPlayer invoke JNI to manipulate client.• The client request to the server to control
hardwares.
Media Framework
Media Framework
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.
Life cycle of activity
Source: Hello Adroid
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
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.
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>
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/
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.
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.
Content manager
• 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.
Source: Google
Service Lifecycle
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