關閉應用程序時出現異常

Question

我有一個音樂播放器應用程序，並且出現問題。當我調用BackPressed或finish（）時，它跳轉到onPause方法不完成（）。爲什麼？我無法完成我的應用程序。非常感謝您的幫助。

我的代碼

public class MusicPlayer extends ThemableActivity implements SeekBar.OnSeekBarChangeListener { 
MediaPlayer musicPlayer; 
int abc; 
@Override 
protected void onCreate(Bundle SavedInstanceState) { 
    super.onCreate(SavedInstanceState); 
    setContentView(R.layout.media_player_layout); 
    Intent intent = getIntent(); 
    String track = intent.getDataString(); 
    TextView txt = (TextView)findViewById(R.id.txt); 
    txt.setGravity(Gravity.CENTER); 
    txt.setText(track); 
    ImageView img = (ImageView)findViewById(R.id.img); 
    img.setLayerType(View.LAYER_TYPE_SOFTWARE, null); 
    final Uri uri = getIntent() != null ? getIntent().getData() : null; 
    final SharedPreferences premiumSettings = getSharedPreferences("PREMIUM", Context.MODE_PRIVATE); 
    final boolean isPremium = premiumSettings.getBoolean("isPremium", false); 
    final SeekBar seekBar = (SeekBar) findViewById(R.id.seekBar); 
    TextView max = (TextView)findViewById(R.id.max); 
    final TextView actual = (TextView)findViewById(R.id.actual); 
    seekBar.setOnSeekBarChangeListener(this); 
    Button loop = (Button)findViewById(R.id.loop); 

    if (isPremium) { 
     musicPlayer = MediaPlayer.create(MusicPlayer.this, uri); 
     musicPlayer.setWakeMode(this.getApplicationContext(), PowerManager.PARTIAL_WAKE_LOCK); 
     seekBar.setMax(musicPlayer.getDuration()); 
     musicPlayer.start(); 
     max.setText(String.format("%dm %ds", 
       TimeUnit.MILLISECONDS.toMinutes((long) musicPlayer.getDuration()), 
       TimeUnit.MILLISECONDS.toSeconds((long) musicPlayer.getDuration()) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) musicPlayer.getDuration())))); 
     final ImageButton play = (ImageButton) findViewById(R.id.play); 
     if(!musicPlayer.isPlaying()){ 

      play.setImageResource(android.R.drawable.ic_media_play); 
     } 
     else{ 
      play.setImageResource(android.R.drawable.ic_media_pause); 

     } 
     play.setOnLongClickListener(new View.OnLongClickListener() { 
      @Override 
      public boolean onLongClick(View view) { 
       if(musicPlayer.isPlaying()){ 
        play.setImageResource(android.R.drawable.ic_media_play); 
        musicPlayer.stop(); 
        return true; 
       } 
       return false; 
      } 
     }); 
     play.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       int position = musicPlayer.getCurrentPosition(); 
       if(musicPlayer.isPlaying()){ 
        musicPlayer.pause(); 
        play.setImageResource(android.R.drawable.ic_media_play); 

       } 
       else if(!musicPlayer.isPlaying()) { 
        musicPlayer.seekTo(position); 
        musicPlayer.start(); 
        play.setImageResource(android.R.drawable.ic_media_pause); 

      }} 
     }); 
     loop.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       musicPlayer.setLooping(true); 
      } 
     }); 
     final Handler mHandler = new Handler(); 
     Runnable mRunnable; 
     mRunnable = new Runnable() { 

      @Override 
      public void run() { 
       int mCurrentPosition = 0; 
       if (musicPlayer != null) { 
        mCurrentPosition = musicPlayer.getCurrentPosition(); 
        seekBar.setProgress(mCurrentPosition); 
       } 
       mHandler.postDelayed(this, 1000); 
       actual.setText(String.format("%dm %ds", 
         TimeUnit.MILLISECONDS.toMinutes((long) mCurrentPosition), 
         TimeUnit.MILLISECONDS.toSeconds((long) mCurrentPosition) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) mCurrentPosition)))); 
      } 
     }; 
     mRunnable.run(); 

     ImageButton exit = (ImageButton) findViewById(R.id.exit); 
     exit.setImageResource(android.R.drawable.btn_dialog); 
     exit.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       if(musicPlayer.isPlaying()) { 
        musicPlayer.setLooping(false); 
        musicPlayer.stop(); 
       } 
       musicPlayer = null; 
       finish(); 

      } 
     }); 


    } 
    else { 
     AlertDialog.Builder builder = new AlertDialog.Builder(MusicPlayer.this); 
     builder.setTitle("Error"); 
     builder.setMessage("You are not premium user. Please enter the promocode or buy the full version"); 
     builder.setIcon(R.drawable.holo_dark_action_info); 
     builder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int whichButton) { 
       finish(); 
      } 
     }); 
     AlertDialog dialog = builder.create(); 
     dialog.show(); 
    }} 
public void onBackPressed() { 
    if(musicPlayer.isPlaying()) { 
     musicPlayer.setLooping(false); 
     musicPlayer.stop(); 
    } 
    musicPlayer = null; 
    finish(); 
} 
@Override 
public void onPause(){ 
    super.onPause(); 
    abc = musicPlayer.getCurrentPosition(); 
    musicPlayer.pause(); 

} 
@Override 
public void onResume(){ 
    super.onResume(); 
    musicPlayer.seekTo(abc); 
    musicPlayer.start(); 
} 
@Override 
public void onProgressChanged(SeekBar seekBar, int i, boolean b) { 
    if (musicPlayer != null && b){ 
     musicPlayer.seekTo(i); 
    } 

} 

@Override 
public void onStartTrackingTouch(SeekBar seekBar) { 

} 

@Override 
public void onStopTrackingTouch(SeekBar seekBar) { 

} 

Answer 1

這是因爲在onPause是，當您退出應用程序之前調用。

請當你打電話的onPause確保musicPlayer不爲空。

@Override 
public void onPause(){ 
    super.onPause(); 
    if(musicPlayer == null) 
     return; 
    abc = musicPlayer.getCurrentPosition(); 
    musicPlayer.pause(); 
} 

此處瞭解詳情：http://developer.android.com/training/basics/activity-lifecycle/stopping.html