无法在音乐播放器应用程序中播放下一首歌曲

Question

我看过一些教程，指出要从原始文件夹播放下一首歌曲，我需要做的就是编写一些代码，例如：

case R.id.next : mp.next();break;"

但是它不起作用。实施 "play previous and play next song" 的正确方法是什么？

这是我的代码供参考：

public class MainActivity extends Activity implements OnClickListener, OnPreparedListener{

private static final String SAVE_POSITION = "MainActivity.SAVE_POSITION";
public static final int STANDARD_NOTIFICATION = 0x01001;
public static final int EXPANDED_NOTIFICATION = 0x01002;
private static final int REQUEST_NOTIFY_LAUNCH = 0;

//Audio Control buttons
Button media;
Button pause;
Button stop;
Button prev;
Button next;
//Media Player
MediaPlayer mp;
boolean mActivityResumed;
boolean mPrepared;
int mAudioPosition;

//array of songs
private int[] rawFiles = {R.raw.black_banquet,R.raw.door_of_holy_spirits,R.raw.castlevania_prologue};
//random playback
private Random random = new Random();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mPrepared = mActivityResumed = false;
    mAudioPosition = 0;

    if(savedInstanceState != null && savedInstanceState.containsKey(SAVE_POSITION)) {
        mAudioPosition = savedInstanceState.getInt(SAVE_POSITION, 0);
    }

    //button audio playback control
    media = (Button) findViewById(R.id.btMedia);
    media.setOnClickListener(this);
    pause = (Button) findViewById(R.id.pause);
    pause.setOnClickListener(this);
    stop = (Button) findViewById(R.id.stop);
    stop.setOnClickListener(this);
    media = (Button) findViewById(R.id.prev);
    media.setOnClickListener(this);
    media = (Button) findViewById(R.id.next);
    media.setOnClickListener(this);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()){
    case R.id.btMedia: if (mp == null){
        mp = new MediaPlayer();
        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mp.setOnPreparedListener(this);

        //random song
        mp = MediaPlayer.create(this, rawFiles[random.nextInt(rawFiles.length)]);
    }
        //looping one song
        mp.setLooping(true);
        mp.start();
          break;
          case R.id.pause : mp.pause();break;
          case R.id.next : mp.next();break;
          case R.id.stop : mp.stop();mp = null;break;
        }


    // Notification Manager
    NotificationManager mgr = 
            (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);

    // Setting the default action.
    NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
    Intent intent = new Intent(this, MainActivity.class);
    PendingIntent pIntent = 
        PendingIntent.getActivity(this, REQUEST_NOTIFY_LAUNCH, intent, 0);
    // Setting the default action.
    builder.setContentIntent(pIntent);
    builder.setSmallIcon(R.drawable.ic_launcher);
    builder.setLargeIcon(BitmapFactory.decodeResource(
        getResources(), R.drawable.ic_launcher));
    builder.setContentTitle("Standard Title");
    builder.setContentText("songTitle");
    mgr.notify(STANDARD_NOTIFICATION, builder.build());

    }


@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if(mp != null) {
        outState.putInt(SAVE_POSITION, mp.getCurrentPosition());
    }
}


@Override
protected void onResume() {
    super.onResume();

    mActivityResumed = true;
    if(mp != null && !mPrepared) {
        mp.prepareAsync();
    } else if(mp != null && mPrepared) {
        mp.seekTo(mAudioPosition);
        mp.start();
    }
}

@Override
protected void onPause() {
    super.onPause();
    mActivityResumed = false;

    if(mp != null && mp.isPlaying()) {
        mp.pause();
    }
}

@Override
protected void onStop() {
    super.onStop();

    if(mp != null && mp.isPlaying()) {
        mp.stop();
        mPrepared = false;
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();

    if(mp != null) {
        mp.release();
    }
}


@Override
public void onPrepared(MediaPlayer mp) {
    // TODO Auto-generated method stub
    mPrepared = true;

    if(mp != null && mActivityResumed) {
        mp.seekTo(mAudioPosition);
        mp.start();
    }

}

Answer 1

对于 Android MediaPlayer class 没有下一个方法。为了实现下一个功能，您需要做的是调用 mp.reset()、mp.setDataSource() 和下一个音频文件，以及 mp.prepare().

E.x.

 case R.id.next : {
     mp.reset();
     mp.setDataSource(**LOCATION OF YOUR AUDIO FILE**) 
     //See http://developer.android.com/reference/android/media/MediaPlayer.html#setDataSource(java.lang.String)
     mp.prepare();
     break;
 }

无法在音乐播放器应用程序中播放下一首歌曲

Unable to play next song in Music Player Application

android

playback

android-mediaplayer