通過廣播Intent控制Android系統自帶的音樂播放器

通過廣播Intent控制Android系統自帶的音樂播放器

ZhengZhiren

http://blog.csdn.net/ZhengZhiRen/archive/2011/01/13/6134730.aspx

Android自帶的音樂播放器隻能算是系統之上的應用，并不包含在SDK中，是以SDK文檔中沒有提及。但是，有時我們需要控制系統音樂播放器的行為，比如切換歌曲、暫停/繼續等。這就隻能從這個應用的源代碼着手了。

這是播放器的代碼樹：

http://android.git.kernel.org/?p=platform/packages/apps/Music.git;a=tree

可以看到，音樂的播放是由MediaPlaybackService這個服務實作的：

http://android.git.kernel.org/?p=platform/packages/apps/Music.git;a=blob;f=src/com/android/music/MediaPlaybackService.java;h=7c0bbedbedef49bf4c38ef97fdcd0f1017bf5d35;hb=HEAD

在服務的onCreate函數中，注冊了IntentFilter和BroadcastReceiver。

public void onCreate() {

super.onCreate();

……

IntentFilter commandFilter = new IntentFilter();

commandFilter.addAction(SERVICECMD);

commandFilter.addAction(TOGGLEPAUSE_ACTION);

commandFilter.addAction(PAUSE_ACTION);

commandFilter.addAction(NEXT_ACTION);

commandFilter.addAction(PREVIOUS_ACTION);

registerReceiver(mIntentReceiver, commandFilter);

……

}

這些Action常量在類的開頭定義為：

public static final String SERVICECMD = "com.android.music.musicservicecommand";

public static final String CMDNAME = "command";

public static final String CMDTOGGLEPAUSE = "togglepause";

public static final String CMDSTOP = "stop";

public static final String CMDPAUSE = "pause";

public static final String CMDPREVIOUS = "previous";

public static final String CMDNEXT = "next";

public static final String TOGGLEPAUSE_ACTION = "com.android.music.musicservicecommand.togglepause";

public static final String PAUSE_ACTION = "com.android.music.musicservicecommand.pause";

public static final String PREVIOUS_ACTION = "com.android.music.musicservicecommand.previous";

public static final String NEXT_ACTION = "com.android.music.musicservicecommand.next";

BroadcastReceiver接收和IntentFilter比對的Intent。根據intent.getAction或intent.getStringExtra("command")的内容，進行相應操作，控制播放器的播放。

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

String action = intent.getAction();

String cmd = intent.getStringExtra("command");

MusicUtils.debugLog("mIntentReceiver.onReceive " + action + " / " + cmd);

if (CMDNEXT.equals(cmd) || NEXT_ACTION.equals(action)) {

next(true);

} else if (CMDPREVIOUS.equals(cmd) || PREVIOUS_ACTION.equals(action)) {

prev();

} else if (CMDTOGGLEPAUSE.equals(cmd) || TOGGLEPAUSE_ACTION.equals(action)) {

if (isPlaying()) {

pause();

mPausedByTransientLossOfFocus = false;

} else {

play();

}

} else if (CMDPAUSE.equals(cmd) || PAUSE_ACTION.equals(action)) {

pause();

mPausedByTransientLossOfFocus = false;

} else if (CMDSTOP.equals(cmd)) {

pause();

mPausedByTransientLossOfFocus = false;

seek(0);

} else if (MediaAppWidgetProvider.CMDAPPWIDGETUPDATE.equals(cmd)) {

// Someone asked us to refresh a set of specific widgets, probably

// because they were just added.

int[] appWidgetIds = intent.getIntArrayExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS);

mAppWidgetProvider.performUpdate(MediaPlaybackService.this, appWidgetIds);

}

}

};

由此，我們可以通過廣播intent控制播放器了：

Intent intent = new Intent("上面那幾個常量");

sendBroadcast(intent);  

參考資料：

http://www.poemcode.net/2009/11/android_music/

http://android.git.kernel.org/?p=platform/packages/apps/Music.git;a=tree