［轉］經過廣播Intent控制Android系統自帶的音樂播放器

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

經過廣播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自帶的音樂播放器只能算是系統之上的應用，並不包含在SDK中，所以SDK文檔中沒有說起。可是，有時咱們須要控制系統音樂播放器的行爲，好比切換歌曲、暫停/繼續等。這就只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

 

能夠看到，音樂的播放是由MediaPlaybackService這個服務實現的：

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，註冊了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爲：

 

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。根據intent.getAction或intent.getStringExtra("command")的內容，進行相應操做，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，咱們能夠經過廣播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