通过广播Intent控制Android系统自带的音乐播放器

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。

[java] view plain copy print ?

publicvoidonCreate(){
super.onCreate();
……
IntentFiltercommandFilter=newIntentFilter();
commandFilter.addAction(SERVICECMD);
commandFilter.addAction(TOGGLEPAUSE_ACTION);
commandFilter.addAction(PAUSE_ACTION);
commandFilter.addAction(NEXT_ACTION);
commandFilter.addAction(PREVIOUS_ACTION);
registerReceiver(mIntentReceiver,commandFilter);
……
}

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：

[java] view plain copy print ?

publicstaticfinalStringSERVICECMD="com.android.music.musicservicecommand";
publicstaticfinalStringCMDNAME="command";
publicstaticfinalStringCMDTOGGLEPAUSE="togglepause";
publicstaticfinalStringCMDSTOP="stop";
publicstaticfinalStringCMDPAUSE="pause";
publicstaticfinalStringCMDPREVIOUS="previous";
publicstaticfinalStringCMDNEXT="next";
publicstaticfinalStringTOGGLEPAUSE_ACTION="com.android.music.musicservicecommand.togglepause";
publicstaticfinalStringPAUSE_ACTION="com.android.music.musicservicecommand.pause";
publicstaticfinalStringPREVIOUS_ACTION="com.android.music.musicservicecommand.previous";
publicstaticfinalStringNEXT_ACTION="com.android.music.musicservicecommand.next";

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。

[java] view plain copy print ?

privateBroadcastReceivermIntentReceiver=newBroadcastReceiver(){
@Override
publicvoidonReceive(Contextcontext,Intentintent){
Stringaction=intent.getAction();
Stringcmd=intent.getStringExtra("command");
MusicUtils.debugLog("mIntentReceiver.onReceive"+action+"/"+cmd);
if(CMDNEXT.equals(cmd)||NEXT_ACTION.equals(action)){
next(true);
}elseif(CMDPREVIOUS.equals(cmd)||PREVIOUS_ACTION.equals(action)){
prev();
}elseif(CMDTOGGLEPAUSE.equals(cmd)||TOGGLEPAUSE_ACTION.equals(action)){
if(isPlaying()){
pause();
mPausedByTransientLossOfFocus=false;
}else{
play();
}
}elseif(CMDPAUSE.equals(cmd)||PAUSE_ACTION.equals(action)){
pause();
mPausedByTransientLossOfFocus=false;
}elseif(CMDSTOP.equals(cmd)){
pause();
mPausedByTransientLossOfFocus=false;
seek(0);
}elseif(MediaAppWidgetProvider.CMDAPPWIDGETUPDATE.equals(cmd)){
//Someoneaskedustorefreshasetofspecificwidgets,probably
//becausetheywerejustadded.
int[]appWidgetIds=intent.getIntArrayExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS);
mAppWidgetProvider.performUpdate(MediaPlaybackService.this,appWidgetIds);
}
}
};

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：

[java] view plain copy print ?

Intentintent=newIntent("上面那几个常量");
sendBroadcast(intent);

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

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