MediaPlayer OnCompletionListener導致錯誤

在我的應用程序中，我創建了一個類來處理播放聲音，它被稱爲SoundPlayer並且擴展AsyncTask以單獨從主線程加載聲音文件。它看起來像這樣：MediaPlayer OnCompletionListener導致錯誤

public class SoundPlayer extends AsyncTask<String, Integer, String> implements 
     OnCompletionListener { 

    private Integer[] soundIDs = {}; 
    private ArrayList<MediaPlayer> sound_player; 
    // private MediaPlayer[] sound_player; 
    private Context context; 
    private static final String DEBUG_TAG = "SoundPlayer"; 
    private Timer timer; 
    private Activity activity; 

    public SoundPlayer(Integer[] soundIDs, Context context, Activity activity) { 
     this.soundIDs = soundIDs; 
     this.context = context; 
     this.activity = activity; 
    } 

    @Override 
    protected String doInBackground(String... params) { 
     sound_player = new ArrayList<MediaPlayer>(); 
     for (int i = 0; i < soundIDs.length; i++) { 
      MediaPlayer temp = new MediaPlayer(); 
      temp = MediaPlayer.create(context, soundIDs[i]); 
      sound_player.add(temp); 
      sound_player.get(i).setOnCompletionListener(SoundPlayer.this); 
     } 
     return null; 
    } 



    @Override 
    public void onCompletion(MediaPlayer mp) { 
     Log.e(DEBUG_TAG, "comp"); 

    } 
}

我從主要活動運行這樣說：當我在我的三星Galaxy Gio的運行appliaction

soundplayer = new SoundPlayer(soundIDs, this, this); 
    soundplayer.execute("");

一切工作正常，但是當我在銀河S2運行它不工作。我注意到，這個問題是在該行：

sound_player.get(i).setOnCompletionListener(SoundPlayer.this);

沒有一切正常（兩臺設備上），但是我必須設置OnCompletionListsner這樣有什麼不對？我也嘗試這樣做：

sound_player.get(i).setOnCompletionListener((OnCompletionListener) context);

並讓我的主要活動實現onCompletionListener方法，但它也不工作。這裏的logcat的：

06-18 16:15:27.835 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:27.865 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:27.900 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:27.905 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:27.905 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:27.905 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:27.950 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:27.990 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:28.005 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:28.005 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:28.035 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:28.035 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:28.060 W/MediaPlayer(20250): info/warning (1, 44) 
06-18 16:15:28.060 I/MediaPlayer(20250): Info (1,44) 
06-18 16:15:28.085 W/MediaPlayer(20250): info/warning (1, 26) 
06-18 16:15:28.085 I/MediaPlayer(20250): Info (1,26) 
06-18 16:15:28.085 E/MediaPlayer(20250): error (1, -17) 
06-18 16:15:28.085 E/MediaPlayer(20250): Error (1,-17) 
06-18 16:15:28.090 D/MediaPlayer(20250): create failed: 
06-18 16:15:28.090 D/MediaPlayer(20250): java.io.IOException: Prepare failed.: status=0x1 
06-18 16:15:28.090 D/MediaPlayer(20250): at android.media.MediaPlayer.prepare(Native Method) 
06-18 16:15:28.090 D/MediaPlayer(20250): at android.media.MediaPlayer.create(MediaPlayer.java:691) 
06-18 16:15:28.090 D/MediaPlayer(20250): at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:36) 
06-18 16:15:28.090 D/MediaPlayer(20250): at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:1) 
06-18 16:15:28.090 D/MediaPlayer(20250): at android.os.AsyncTask$2.call(AsyncTask.java:185) 
06-18 16:15:28.090 D/MediaPlayer(20250): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
06-18 16:15:28.090 D/MediaPlayer(20250): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
06-18 16:15:28.090 D/MediaPlayer(20250): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
06-18 16:15:28.090 D/MediaPlayer(20250): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
06-18 16:15:28.090 D/MediaPlayer(20250): at java.lang.Thread.run(Thread.java:1019)

和

06-18 16:25:10.330 W/MediaPlayer(21988): info/warning (1, 26) 
06-18 16:25:10.330 E/MediaPlayer(21988): error (1, -17) 
06-18 16:25:10.335 I/MediaPlayer(21988): Info (1,26) 
06-18 16:25:10.335 E/MediaPlayer(21988): Error (1,-17) 
06-18 16:25:10.335 D/MediaPlayer(21988): create failed: 
06-18 16:25:10.335 D/MediaPlayer(21988): java.io.IOException: Prepare failed.: status=0x1 
06-18 16:25:10.335 D/MediaPlayer(21988): at android.media.MediaPlayer.prepare(Native Method) 
06-18 16:25:10.335 D/MediaPlayer(21988): at android.media.MediaPlayer.create(MediaPlayer.java:691) 
06-18 16:25:10.335 D/MediaPlayer(21988): at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:38) 
06-18 16:25:10.335 D/MediaPlayer(21988): at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:1) 
06-18 16:25:10.335 D/MediaPlayer(21988): at android.os.AsyncTask$2.call(AsyncTask.java:185) 
06-18 16:25:10.335 D/MediaPlayer(21988): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
06-18 16:25:10.335 D/MediaPlayer(21988): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
06-18 16:25:10.335 D/MediaPlayer(21988): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
06-18 16:25:10.335 D/MediaPlayer(21988): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
06-18 16:25:10.335 D/MediaPlayer(21988): at java.lang.Thread.run(Thread.java:1019) 
06-18 16:25:10.335 W/dalvikvm(21988): threadid=8: thread exiting with uncaught exception (group=0x4001e578) 
06-18 16:25:10.340 E/AndroidRuntime(21988): FATAL EXCEPTION: AsyncTask #1 
06-18 16:25:10.340 E/AndroidRuntime(21988): java.lang.RuntimeException: An error occured while executing doInBackground() 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at android.os.AsyncTask$3.done(AsyncTask.java:200) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.FutureTask.setException(FutureTask.java:125) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.lang.Thread.run(Thread.java:1019) 
06-18 16:25:10.340 E/AndroidRuntime(21988): Caused by: java.lang.NullPointerException 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:40) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at com.artostolab.scaryringtones.SoundPlayer.doInBackground(SoundPlayer.java:1) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at android.os.AsyncTask$2.call(AsyncTask.java:185) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
06-18 16:25:10.340 E/AndroidRuntime(21988):  ... 4 more 
06-18 16:25:10.345 E/  (2696): Dumpstate > /data/log/dumpstate_app_error 
06-18 16:25:10.345 W/ActivityManager(2696): Force finishing activity com.artostolab.scaryringtones/.MainList

感謝您的幫助

來源

2013-06-18 Janek

我自己找到了一個解決方案，不知道爲什麼，但是在doInBackground方法裏面設置onCompletionListener會在一些設備上導致空指針異常，所以我想通過這個方法設置OnCompletionListner以外，例如當你想玩聲音和它的工作

來源

2013-06-19 11:24:12 Janek

我認爲正在發生的事情是，你的電話MediaPlayer.create(context, soundIDs[i]);失敗（見堆棧跟蹤 - 「java.io.IOException異常：準備失敗「），因此temp爲空。

創建許多MediaPlayer實例可能是根本原因。我有一個應用程序，可以播放單個聲音樣本的序列，並可以隨時創建我的實例。

來源

2013-06-18 14:55:56 Phil

但它沒有發生的時候我不使用這行：「sound_player.get（I）.setOnCompletionListener（SoundPlayer.this）;」沒有它一切正常，所以我認爲這個問題不是在創建許多MediaPlayer實例 – Janek

是的但（假設我的理論是正確的），你只是把一個空值到數組中，所以sound_player.get（i）將返回null，並且你正在對null對象調用setOnCompletionListener，因此NPE ... – Phil

這將被糾正，但我測試了它，並嘗試使用這個數組播放聲音，它工作正常，所以我認爲這不是問題 – Janek

MediaPlayer OnCompletionListener導致錯誤

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