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1. App installation on external storage media   把应用安装在外部存储器（SD卡）

http://androidappdocs.appspot.com/guide/appendix/install-location.html

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    android:installLocation="preferExternal"
    ... >

2. Data backup  用户数据备份

http://androidappdocs.appspot.com/guide/topics/data/backup.html

<manifest ... >
    <application android:label="MyApplication"
                 android:backupAgent="MyBackupAgent">
        <activity ... >
            ...
        </activity>
    </application>
</manifest>

3. Graphics 增强了图形处理的功能，特别是3D性能得到大幅度提升

• New OpenGL ES 2.0 APIs in android.opengl.GLES20.
• New ETC1, ETC1Util, and ETC1Util.ETC1Texture classes and utility methods for using ETC1 for texture compression.
• New ImageFormat class.
• New YUV image format API to enable compression from YUV to JPEG and manipulation of YUV data.

4. Media

• New APIs in android.media.AudioManager for managing audio focus, transport control, transient loss of audio focus, ducking.
• New broadcast intent for routing audio to SCO — ACTION_SCO_AUDIO_STATE_CHANGED with extras indicating new state.
• New APIs in SoundPool to detect completion of sound-loading.
• New APIs in SoundPool for auto pause and resume.
• New APIs in MediaRecorder for specifying audio settings for number of channels, encoding and sampling rates, sampling rate.
• New APIs for adding files to the media database, so that they are automatically scanned. SeeMediaScannerConnection.scanFile and MediaScannerConnection.OnScanCompletedListener.

5. Speech recognition and third-party recognition engines

• The platform provides new speech-recognition APIs that allow applications to have a richer interaction with the available voice recognizer. For example, the APIs are sufficient to integrate voice recognition deeply into an IME.
• The platform also provides a RecognitionService base class that lets third-party developers create plug-in recognition engines.
• New RecognitionListener interface to receive callbacks.
• New RecognizerIntent extras that let a requester app specify details as preferred language, minimum length in milliseconds, and so on.

6. Camera and camcorder

• Changes to camera preview API to improve efficieny of preview pipeline.
• New display orientation for camera (it can now work in portrait orientation).
• New APIs in android.hardware.Camera for managing zoom level.
• New APIs android.hardware.Camera.Parameters for querying and setting device camera settings such as focal length, exposure, zoom level, view angle, and others.
• New thumbnail utility for video and image thumbnails.
• New CamcorderProfile and CamcorderProfile classes enable apps to determine device hardware camera capablities.
• New support in android.media.ExifInterface for retrieving GPS and focal length.

7. Device policy manager

New device policy management APIs allow developers to write "device administrator" applications that can control security features of the device, such as the minimum password strength, data wipe, and so on. Users can select the administrators that are enabled on their devices. For more information, see the android.app.admin classees or the example application code inDeviceAdminSample.java.

8. UI Framework

• New UI modes "car mode" and "night mode" and UiModeManager let applications adjust their application UI for specific user modes.
• New ScaleGestureDetector that lets Views detect and handle transformation gestures that involve more than one pointer (multitouch) using the supplied MotionEvents.
• Improvements in the way that multitouch events are reported in MotionEvent objects.
• The layout attribute fill_parent is renamed to match_parent. This affects both XML and Java code (seeViewGroup.LayoutParams). Note that the platform will continue to honor uses of fill_parent in legacy applications.
• New layout attributes tabStripEnabled, tabStripRight, and tabStripLeft let developers customize the bottom strip of TabWidgets.
• Better support for managed dialogs in Activity.

9. Accounts and sync

• New method AddPeriodicSync() lets you schedule a periodic sync with a specific account, authority, and extras at the given frequency.

10. New manifest elements and attributes

• For specifying the application's preferred install location (see App Installation on External Storage Media, above):
  • New android:installLocation attribute of the <manifest> element. Specifies the default install location defined by an application.
• For managing user data backup (see Backup manager, above, for more information):
  • New android:backupAgent attribute of the <application> element. Specifies the component name of the BackupAgent subclass provided by the application to handle backup/restore operations, if any.
  • New android:restoreAnyVersion attribute of the <application> element. Boolean value that indicates whether the application is prepared to attempt a restore of any backed-up dataset, even if the backup is apparently from a newer version of the application than is currently installed on the device.
• For managing the platform's JIT compiler:
  • New android:vmSafeMode attribute of the <application> element. Boolean value that specifies whether to disable JIT compiler optimizations when running the application.

11. Permissions

• android.permission.BIND_DEVICE_ADMIN — Any device administration broadcast receiver must require this permission, to ensure that only the system can interact with it.
• android.permission.KILL_BACKGROUND_PROCESSES — Allows an application to callkillBackgroundProcesses(String).
• android.permission.BIND_WALLPAPER — Any WallpaperService must require this permission, to ensure that only the system can interact with it.
• android.permission.SET_TIME — Allows an application to set the system time.