关闭应用程序时获取异常

Question

我有一个音乐播放器应用程序，我有一个问题。当我调用BackPressed或finish（）时，它跳转到onPause方法不完成（）。为什么？我无法完成我的应用程序。非常感谢你的帮助。

我的代码

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

那是因为在退出应用程序之前调用了onPause。

确保在调用onPause时，musicPlayer不为空。

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

此处有更多信息：http://developer.android.com/training/basics/activity-lifecycle/stopping.html