1.傳送系統廣播：
Intent i = new Intent(“com.android.music.musicservicecommand”);
i.putExtra(“command”, “pause”);
context.sendBroadcast(i);
因為其他的播放器不一定註冊監聽了那個廣播，所以大多數情況是不起作用的。

2.通過觸發媒體的按鈕來操作播放器狀態:
KeyEvent.KEYCODE_MEDIA_PAUSE
public static void sendMediaButton(Context context, int keyCode) {
AudioManager audioManager= (AudioManager) context.getSystemService (Context.AUDIO_SERVICE);
//先判斷後臺是否再播放音樂
if (audioManager.isMusicActive()){
KeyEvent keyEvent = new KeyEvent(KeyEvent.ACTION_DOWN, keyCode);
Intent intent = new Intent(Intent.ACTION_MEDIA_BUTTON);
intent.putExtra(Intent.EXTRA_KEY_EVENT, keyEvent);
context.sendOrderedBroadcast(intent,null);

    keyEvent = new KeyEvent(KeyEvent.ACTION_UP, keyCode);
    intent = new Intent(Intent.ACTION_MEDIA_BUTTON);
    intent.putExtra(Intent.EXTRA_KEY_EVENT, keyEvent);
    context.sendOrderedBroadcast(intent,null);
}

}

3. 通過AudioManager獲取音訊焦點AudioFocus，來競爭使用audio做停止播放或者降低聲音的處理
AudioManager am = (AudioManager) mAppContext.getSystemService (Context.AUDIO_SERVICE);
am.requestAudioFocus(null, AudioManager.STREAM_MUSIC, AudioManager .AUDIOFOCUS_GAIN_TRANSIENT);
AudioManager.AUDIOFOCUS_GAIN： 永久獲取媒體焦點（播放音樂） 估計音樂播放器使用了此方法，在播放視訊時呼叫，不起作用
AudioManager.AUDIOFOCUS_GAIN_TRANSIENT 暫時獲取焦點 適用於短暫的音訊
AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK Duck 我們應用跟其他應用共用焦點 我們播放的時候其他音訊會降低音量

後臺播放音樂時，專案中播放視訊，1方法不起作用，2方法有效 3 暫時獲取焦點時，播放視訊，音樂停止，退出播放介面，音樂自動播放

4.寫一個服務，當第三方播放器開啟時 ，開啟這個服務，音樂暫停；關閉服務，音樂繼續
服務類：
private AudioManager mAm;
private static boolean vIsActive=false;
private MyOnAudioFocusChangeListener mListener;
public class MyOnAudioFocusChangeListener implements OnAudioFocusChangeListener {
@Override
public void onAudioFocusChange(int focusChange) {
// TODO Auto-generated method stub
}
}
public int onStartCommand(Intent intent, int flags, int startId) {
// TODO Auto-generated method stub
Log.d(TAG, “onStartCommand”);
Toast.makeText(getApplicationContext(), “服務已啟動”, 0).show();

            mAm = (AudioManager) getApplicationContext().getSystemService(  
                    Context.AUDIO_SERVICE);  
            vIsActive=mAm.isMusicActive();  
            mListener = new MyOnAudioFocusChangeListener();  
            if(vIsActive)  
            {  
                int result = mAm.requestAudioFocus(mListener,  
                        AudioManager.STREAM_MUSIC,  
                        AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);  

                if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED)    
                {    
                    Log.d(TAG, "requestAudioFocus successfully.");                                    
                }    
                else    
                {    
                    Log.d(TAG, "requestAudioFocus failed.");    
                }    
            }                 
            return super.onStartCommand(intent, flags, startId);  
        }  

    @Override  
    public void onDestroy() {  
        // TODO Auto-generated method stub  
        super.onDestroy();  
        if(vIsActive)  
        {  
            mAm.abandonAudioFocus(mListener);  
        }  
        Log.d(TAG, "onDestroy");  
    }  

呼叫：開始或結束服務
startService(new Intent(MainActivity.this,StartService.class));
stopService(new Intent(MainActivity.this,StartService.class));