Mediaplayer跟蹤改變問題

Question

這是我的代碼來播放和更新跟蹤和按鈕點擊我呼籲update()功能，但軌道沒有正確改變。

第一首曲目播放得很好，但當我嘗試切換到下一首時，它的行爲不正確，我錯了。

MediaPlayer mPlayer; 


     @Override 
     public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     mPlayer=new MediaPlayer(); 
     mPlayer.setOnPreparedListener(this); 
     } 

     public void prepareMediaPlayer(FileDescriptor fd) 
     { 
      try { 
       mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC); 
       Log.d("player", "setAudiotStreamType"); 
       mPlayer.setDataSource(fd); 
       Log.d("player", "setDataSource"); 
       mPlayer.prepareAsync(); 
       Log.d("player", "prepareAsync"); 

      } 
      catch (IOException e) {} 
      catch (IllegalArgumentException e) {} 
      catch (IllegalStateException e) {} 
     } 

     @Override 
     public void onPrepared(MediaPlayer arg0) { 
     } 

     public void updateTrack() 
     { 
         File f=(File) imageFilexxSm.values().toArray()[index]; 
        FileInputStream inputStream = new FileInputStream(f); 
        prepareMediaPlayer(inputStream.getFD()); 
        inputStream.close(); 

        if(mPlayer.isPlaying()) 
        { 
        mPlayer.stop(); 
        mPlayer.reset(); 
        mPlayer.reset(); 
        } 

        else 
        { 
        mPlayer.start();  
        } 

     } 

登錄：

05-11 13:17:42.782: E/MediaPlayer(14969): start called in state 4 
05-11 13:17:42.782: E/MediaPlayer(14969): error (-38, 0) 
05-11 13:17:42.821: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.372MB for 4194320-byte allocation 
05-11 13:17:43.040: I/System.out(14969): index value is 0/1024/0 
05-11 13:17:43.087: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.457MB for 2261008-byte allocation 
05-11 13:17:43.189: E/MediaPlayer(14969): attachNewPlayer called in state 8 
05-11 13:17:43.220: I/Choreographer(14969): Skipped 35 frames! The application may be doing too much work on its main thread. 
05-11 13:17:43.275: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.452MB for 4194320-byte allocation 
05-11 13:17:43.392: I/MediaPlayer(14969): Don't send intent. msg.arg1 = 0, msg.arg2 = 0 
05-11 13:17:43.392: E/MediaPlayer(14969): Error (-38,0) 
05-11 13:17:57.642: I/System.out(14969): action down 
05-11 13:17:57.642: I/System.out(14969): points 1.6014493?21 
05-11 13:17:57.642: I/System.out(14969): show one page 
05-11 13:17:57.642: I/System.out(14969): start curl right 
05-11 13:17:57.650: I/System.out(14969): index value is 1/1024/1 
05-11 13:17:57.681: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.401MB for 2261008-byte allocation 
05-11 13:17:57.775: E/MediaPlayer(14969): attachNewPlayer called in state 128 
05-11 13:17:57.821: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.401MB for 4194320-byte allocation 
05-11 13:18:04.704: I/System.out(14969): action down 
05-11 13:18:04.704: I/System.out(14969): points 1.692029?21 
05-11 13:18:04.704: I/System.out(14969): show one page 
05-11 13:18:04.704: I/System.out(14969): start curl right 
05-11 13:18:04.704: I/System.out(14969): index value is 2/1024/2 
05-11 13:18:04.736: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.315MB for 2261008-byte allocation 
05-11 13:18:04.829: E/MediaPlayer(14969): attachNewPlayer called in state 128 
05-11 13:18:04.876: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.316MB for 4194320-byte allocation 
05-11 13:18:08.845: I/System.out(14969): action down 
05-11 13:18:08.845: I/System.out(14969): points 1.5471015?21 
05-11 13:18:08.845: I/System.out(14969): show one page 
05-11 13:18:08.845: I/System.out(14969): start curl right 
05-11 13:18:08.845: I/System.out(14969): index value is 3/1024/3 
05-11 13:18:08.876: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.316MB for 2261008-byte allocation 
05-11 13:18:08.970: E/MediaPlayer(14969): attachNewPlayer called in state 16 
05-11 13:18:09.025: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.316MB for 4194320-byte allocation 
05-11 13:18:12.892: I/System.out(14969): action down 
05-11 13:18:12.892: I/System.out(14969): points 1.5688405?21 
05-11 13:18:12.892: I/System.out(14969): show one page 
05-11 13:18:12.892: I/System.out(14969): start curl right 
05-11 13:18:12.892: I/System.out(14969): index value is 4/1024/4 
05-11 13:18:12.923: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.316MB for 2261008-byte allocation 
05-11 13:18:13.025: E/MediaPlayer(14969): start called in state 4 
05-11 13:18:13.025: E/MediaPlayer(14969): error (-38, 0) 
05-11 13:18:13.064: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.316MB for 4194320-byte allocation 
05-11 13:18:13.126: E/MediaPlayer(14969): Error (-38,0) 
05-11 13:18:13.126: I/MediaPlayer(14969): Don't send intent. msg.arg1 = 0, msg.arg2 = 0 
05-11 13:18:18.228: I/System.out(14969): action down 
05-11 13:18:18.236: I/System.out(14969): points -1.5289855?21 
05-11 13:18:18.236: I/System.out(14969): show one page 
05-11 13:18:18.236: I/System.out(14969): index value is 3/1024/3 
05-11 13:18:18.259: I/dalvikvm-heap(14969): Grow heap (frag case) to 30.316MB for 2261008-byte allocation 
05-11 13:18:18.353: E/MediaPlayer(14969): attachNewPlayer called in state 8 
05-11 13:18:18.400: I/dalvikvm-heap(14969): Grow heap (frag case) to 34.316MB for 4194320-byte allocation 

Answer 1

兩件事伸出：

1. 您使用prepareAsync，這是異步。也就是說，您應該等待onPrepared回調，然後再執行任何依賴準備完成的任務（如致電start）。這就是爲什麼你得到「start called in state 4」錯誤信息（狀態4是MEDIA_PLAYER_PREPARING）。

2. 如果在正在進行的回放過程中調用updateTrack，在爲新歌準備前似乎沒有停止MediaPlayer。撥打電話prepareMediaPlayer後，您已撥打電話stop，但這對您不會有什麼好處。爲了能夠重新準備球員，您必須首先stop，如果您還想更改數據源，您必須在停止球員後reset。

有關一組有效狀態轉換請參閱MediaPlayer documentation's state diagram。