Android为什么要用服务播放音乐不用子线程

1. 对于控制研究媒体播放器，通过本地服务打，不如送媒体播放器参考其他类一样CarefulMediaPlayer（MP，这一点）;你在处理此类播放器的属性。我认为它帮助你。 谢谢 2. 我为这个问题挣扎，最后我得到了它的工作班以下。这个想法是一个线程与活套，剩下活着，并处理所有的MediaPlayer的逻辑。 我只退出尺蠖和清理线程，如果服务接收到的明确 public class PlayService extends IntentService { private static PowerManager.WakeLock wakeLock; private static final String TAG = "PlayService"; private static String LOCK_NAME = TAG; public static final String EXTRA_FILE = "file"; public static final String ACTION_PLAY = "play"; private static final String ACTION_STOP = "stop"; public static final int MSG_START = 1; public static final int MSG_STOP = 2; public PlayService(String name) { super(name); } public PlayService() { super("PlayService"); } @Override public void onCreate() { super.onCreate(); } @Override protected void onHandleIntent(Intent intent) { Message msg = new Message(); if (ACTION_PLAY.equalsIgnoreCase(intent.getAction())) { String fileName = intent.getExtras().getString(EXTRA_FILE); msg.what = MSG_START; msg.obj = fileName; } else if (ACTION_STOP.equalsIgnoreCase(intent.getAction())) { msg.what = MSG_STOP; } try { PlayMediaThread.getInstance(this).sendMessage(msg); } catch (InterruptedException e) { Log.e(TAG, e.getMessage()); } } public static PowerManager.WakeLock acquireLock(Context context) { if (wakeLock == null !wakeLock.isHeld()) { PowerManager powerManager = (PowerManager) context .getSystemService(Context.POWER_SERVICE); wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, LOCK_NAME); wakeLock.setReferenceCounted(true); wakeLock.acquire(); } return wakeLock; } public static void releaseLock(Context context) { if (wakeLock != null && wakeLock.isHeld()) { wakeLock.release(); } } } class PlayMediaThread extends Thread implements OnCompletionListener, OnErrorListener, OnPreparedListener { private static Semaphore semaphore = new Semaphore(0); private static Handler handler; private static Looper myLooper; private static Context context; private static String currentFileName; private static MediaPlayer player; private static PlayMediaThread instance; private static final String TAG = "PlayMediaThread"; private PlayMediaThread(Context context) throws InterruptedException { super(TAG); PlayMediaThread.context = context; start(); // To insure that the looper was initialized correctly before return an // instance semaphore.acquire(); } public static PlayMediaThread getInstance(Context context) throws InterruptedException { if (instance == null) { instance = new PlayMediaThread(context); } PlayMediaThread.context = context; return instance; } public void sendMessage(Message msg) { handler.sendMessage(msg); } public void quitLooper() { try { if (myLooper != null) { myLooper.quit(); Log.i(TAG, "After quit"); } } catch (Exception ex) { Log.e(TAG, ex.getMessage()); } } @Override public void run() { Looper.prepare(); myLooper = Looper.myLooper(); handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what == PlayService.MSG_START) { startPlayer((String) msg.obj); } else if (msg.what == PlayService.MSG_STOP) { // when stop command is coming from the activity i.e. user // explicitly clicked stop, I quit the looper and // clean the thread stopPlayer(true); } } }; semaphore.release(); Log.i(TAG, "Before Loop"); Looper.loop(); } private void stopPlayer(boolean clean) { if (player != null) { if (player.isPlaying()) { player.stop(); } player.release(); player = null; } if (clean) { PlayService.releaseLock(context); quitLooper(); instance = null; } } private void startPlayer(String fileName) { if (player != null && player.isPlaying() && currentFileName != null && currentFileName.equalsIgnoreCase(fileName)) { return; } currentFileName = fileName; stopPlayer(false); player = new MediaPlayer(); player.setOnCompletionListener(this); player.setOnErrorListener(this); player.setOnPreparedListener(this); try { player.setDataSource(context, Uri.parse(currentFileName)); player.prepare(); player.start(); PlayService.acquireLock(context); } catch (Exception e) { Log.e(TAG, e.getMessage()); } } @Override public boolean onError(MediaPlayer mp, int arg1, int arg2) { Log.e(TAG, "onError"); stopPlayer(true); return false; } @Override public void onCompletion(MediaPlayer mp) { Log.d(TAG, "onCompletion"); // Just to quit the looper and clean the thread stopPlayer(true); } @Override public void onPrepared(MediaPlayer mp) { Log.d(TAG, "onPrepared"); } }