私がアンドロイドアプリでのMediaPlayerで間違ってやっている何

MediaPlayer easysong; 
MediaPlayer normalsong; 
MediaPlayer hardsong; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.land_main); 

    btn3 = (Button)findViewById(R.id.button3); 
    restartButton = (Button)findViewById(R.id.restartButton); 
} 
@Override 
public void onClick(View v) { 
    easysong = MediaPlayer.create(MainActivity.this, R.raw.arideniro); 
    normalsong = MediaPlayer.create(MainActivity.this, R.raw.junior); 
    hardsong = MediaPlayer.create(MainActivity.this, R.raw.ketsathis); 
    if (v == btn3) { 
     btn3.setVisibility(View.GONE); 
     new Thread(new Runnable() { 
      public void run() { 
       if(mstop==1){ 
        if(i==500){ 
         easysong.start();} 
        else if(i==375){ 
         normalsong.start(); 
        }else if(i==250){ 
         hardsong.start(); 
        }} 
       while (counter > 0) { 
        try { 

         Thread.sleep(i); 
        } catch (InterruptedException e) { 
         e.printStackTrace(); 
        } 
        counter--; 
        runOnUiThread(new Runnable() { 
         @Override 
         public void run() { 
          scoreText.setText(Integer.toString(counter)); 
         } 
        }); 
        if(i>150){ 
         i/=1.01;} 
        else if((i>90-(dif/10))){ 
         i-=1; 
        } 
       }if (counter==0) { 
        mChronometer.stop(); 
        playerStop(); 

        runOnUiThread(new Runnable() { 
         @Override 
         public void run() { 
          restartButton.setVisibility(View.VISIBLE); 
         } 
        }); 
       } 
      } 
     }).start(); 
    } 
    if(v == restartButton){ 
     counter = 101; 
     i = 500 - dif; 
     new Thread(new Runnable() { 

      public void run() { 
       if(i==500){ 
        easysong.start();} 
       else if(i==375){ 
        normalsong.start(); 
       }else if(i==250){ 
        hardsong.start(); 
       } 
       while (counter > 0) { 
        try { 

         Thread.sleep(i); 
        } catch (InterruptedException e) { 
         e.printStackTrace(); 
        } 
        counter--; 
        runOnUiThread(new Runnable() { 
         @Override 
         public void run() { 
          scoreText.setText(Integer.toString(counter)); 
         } 
        }); 
        if(i>150){ 
         i/=1.01;} 
        else if(i>90-(dif/10)){ 
         i-=1; 
        } 
       }if (counter==0) { 
        playerStop(); 
        runOnUiThread(new Runnable() { 
         @Override 
         public void run() { 
          restartButton.setVisibility(View.VISIBLE); 
         } 
        }); 
       } 
      } 
     }).start(); 
     restartButton.setVisibility(View.GONE); 
    } 

} 
public void updateTimerText(final String time){ 
    runOnUiThread(new Runnable() { 
     @Override 
     public void run() { 
      mTvTime.setText(time); 
     } 
    }); 
} 
@Override 
public void onUserLeaveHint() {  // This is to stop the music if user presses home button 
    if(easysong.isPlaying()) { 
     easysong.stop(); 
     easysong.release(); 
     easysong = null; 
    } else if(normalsong.isPlaying()) { 
     normalsong.stop(); 
     normalsong.release(); 
     normalsong = null; 
    } 
    else if (hardsong.isPlaying()){ 
     hardsong.stop(); 
     hardsong.release(); 
     hardsong = null; 
    } 
} 
public void playerStop(){ 
    if (easysong.isPlaying()) { 
     easysong.stop(); 
     easysong.release(); 
     easysong = null; 
    }else if (normalsong.isPlaying()) { 
     normalsong.stop(); 
     normalsong.release(); 
     normalsong = null; 
    }else if (hardsong.isPlaying()) { 
     hardsong.stop(); 
     hardsong.release(); 
     hardsong = null; 
    } 
}

問題は、メディアプレーヤから来て、これは、アプリケーションがフリーズしてもいくつかの点で、私のアプリケーションでそれのためのすべてのコードをある、または歌はいつもませんカウンターが0になると停止します。これは私が直面しているエラーで、いくつかのことを試しましたが、もう何をすべきか分かりません。それで私は何を間違えたのですか？そして、私が間違っていたこととは別に、家のボタンを押しても音楽を止めるようにしましたが、戻るボタンを押すと止める方法はありますか？私がアンドロイドアプリでのMediaPlayerで間違ってやっている何

12-23 23:28:19.780 8897-8897/com.example.user.myapplication D/MediaPlayer: setSubtitleAnchor in MediaPlayer 
12-23 23:28:35.193 8897-8897/com.example.user.myapplication W/MediaPlayer: mediaplayer went away with unhandled events 
12-23 23:33:21.518 8897-8897/com.example.user.myapplication D/MediaPlayer: create failed: 
java.io.IOException: Prepare failed.: status=0x80000000 
at android.media.MediaPlayer._prepare(Native Method) 
at android.media.MediaPlayer.prepare(MediaPlayer.java:1184) 
at android.media.MediaPlayer.create(MediaPlayer.java:943) 
at android.media.MediaPlayer.create(MediaPlayer.java:914) 
at com.example.user.myapplication.MainActivity.onClick(MainActivity.java:114) 
at android.view.View.performClick(View.java:5637) 
at android.view.View$PerformClick.run(View.java:22429) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6119) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

12-23 23:33:22.163 8897-21377/com.example.user.myapplication E/AndroidRuntime: FATAL EXCEPTION: Thread-11 
Process: com.example.user.myapplication, PID: 8897 
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.media.MediaPlayer.isPlaying()' on a null object reference 
at com.example.user.myapplication.MainActivity.playerStop(MainActivity.java:207) 
at com.example.user.myapplication.MainActivity$2.run(MainActivity.java:167) 
at java.lang.Thread.run(Thread.java:761)

出典

2016-12-23 Tom1