［转］通过广播Intent控制Android系统自带的音乐播放器

转自http://blog.csdn.net/zhengzhiren/article/details/6134730

通过广播Intent控制Android系统自带的音乐播放器

ZhengZhiren

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

 

Android自带的音乐播放器只能算是系统之上的应用，并不包含在SDK中，因此SDK文档中没有提及。但是，有时我们需要控制系统音乐播放器的行为，比如切换歌曲、暂停/继续等。这就只能从这个应用的源代码着手了。

这是播放器的代码树：

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

可以看到，音乐的播放是由MediaPlaybackService这个服务实现的：

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

在服务的onCreate函数中，注册了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);
    ……
}

这些Action常量在类的开头定义为：

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匹配的Intent。根据intent.getAction或intent.getStringExtra("command")的内容，进行相应操作，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，我们可以通过广播intent控制播放器了：

Intent intent = new Intent("上面那几个常量");
sendBroadcast(intent);

  

参考资料：

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

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