java - Android Studio music player list 查看播放列表

Question

对于这个笨拙的问题，我深表歉意，但我正在 android studio 中构建一个音乐播放器，我遇到了歌曲像播放列表一样一首接一首播放的问题。歌曲只能手动挑选，歌曲结束后它就会停止，直到用户点击另一首歌曲。我写了两段代码，我怀疑它们可以解决这个问题，但我不确定如何实现它们，或者它们最终是否会有任何用处。我真的很感激这方面的帮助，真的可以使用它。任何建议或建设性的批评总是受欢迎的，在此先感谢。以下是 fragment :

//------------> to get the next song <---------------
int itemsInList=list.getAdapter().getCount();
for(int i=1;i<itemsInList;i++){
    list.setSelection(i);
}
//--------------> to play the song on list item click <-------------------
@Override
protected void onListItemClick(ListView list, View view, int position,
long id) {
    super.onListItemClick(list, view, position, id);
    currentFile = (String) view.getTag();
    startPlay(currentFile);
}

这里仅供引用是我的主要 java 文件:

public class MainActivity extends ListActivity {

private static final int UPDATE_FREQUENCY = 500;
private static final int STEP_VALUE = 4000;

private MediaCursorAdapter mediaAdapter = null;
private TextView selectedFile = null;
private SeekBar seekbar = null;
private MediaPlayer player = null;
private ListView list = null;
private ImageButton playButton = null;
private ImageButton prevButton = null;
private ImageButton nextButton = null;
private ImageButton btNext = null;
private ImageButton btPrev = null;

private boolean isStarted = true;
private String currentFile = "";
private boolean isMovingSeekBar = false;

private final Handler handler = new Handler();

private final Runnable updatePositionRunnable = new Runnable() {
    public void run() {
        updatePosition();
    }
};

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

    selectedFile = (TextView) findViewById(R.id.selectedfile);
    seekbar = (SeekBar) findViewById(R.id.seekbar);
    playButton = (ImageButton) findViewById(R.id.play);
    prevButton = (ImageButton) findViewById(R.id.prev);
    nextButton = (ImageButton) findViewById(R.id.next);
    btNext = (ImageButton) findViewById(R.id.btNxt);
    btPrev = (ImageButton) findViewById(R.id.btPrev);

    player = new MediaPlayer();

    player.setOnCompletionListener(onCompletion);
    player.setOnErrorListener(onError);
    seekbar.setOnSeekBarChangeListener(seekBarChanged);

    Cursor cursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null, null);

    if (null != cursor) {
        cursor.moveToFirst();

        mediaAdapter = new MediaCursorAdapter(this, R.layout.list_item, cursor);

        setListAdapter(mediaAdapter);

        playButton.setOnClickListener(onButtonClick);
        nextButton.setOnClickListener(onButtonClick);
        prevButton.setOnClickListener(onButtonClick);
        btNext.setOnClickListener(onButtonClick);
        btPrev.setOnClickListener(onButtonClick);

    }
}

//----------- ??? ----------------------------------------------------------------
int itemsInList=list.getAdapter().getCount();
for(int i=1;i<itemsInList;i++){
    list.setSelection(i);
}

@Override
protected void onListItemClick(ListView list, View view, int position, long id) {
    super.onListItemClick(list, view, position, id);
    currentFile = (String) view.getTag();
    startPlay(currentFile);
}
// --------------------------------------------------------------------------------

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

    handler.removeCallbacks(updatePositionRunnable);
    player.stop();
    player.reset();
    player.release();

    player = null;
}

private void startPlay(String file) {
    Log.i("Selected: ", file);

    selectedFile.setText(file);
    seekbar.setProgress(0);

    player.stop();
    player.reset();

    try {
        player.setDataSource(file);
        player.prepare();
        player.start();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    seekbar.setMax(player.getDuration());
    playButton.setImageResource(android.R.drawable.ic_media_pause);

    updatePosition();

    isStarted = true;
}

private void stopPlay() {
    player.stop();
    player.reset();
    playButton.setImageResource(android.R.drawable.ic_media_play);
    handler.removeCallbacks(updatePositionRunnable);
    seekbar.setProgress(0);

    isStarted = false;
}

private void updatePosition() {
    handler.removeCallbacks(updatePositionRunnable);

    seekbar.setProgress(player.getCurrentPosition());

    handler.postDelayed(updatePositionRunnable, UPDATE_FREQUENCY);
}

private class MediaCursorAdapter extends SimpleCursorAdapter {

    public MediaCursorAdapter(Context context, int layout, Cursor c) {
        super(context, layout, c,
                new String[]{MediaStore.MediaColumns.DISPLAY_NAME, MediaStore.MediaColumns.TITLE, MediaStore.Audio.AudioColumns.DURATION},
                new int[]{R.id.displayname, R.id.title, R.id.duration});
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        TextView title = (TextView) view.findViewById(R.id.title);
        TextView name = (TextView) view.findViewById(R.id.displayname);
        TextView duration = (TextView) view.findViewById(R.id.duration);

        name.setText(cursor.getString(
                cursor.getColumnIndex(MediaStore.MediaColumns.DISPLAY_NAME)));

        title.setText(cursor.getString(
                cursor.getColumnIndex(MediaStore.MediaColumns.TITLE)));

        long durationInMs = Long.parseLong(cursor.getString(
                cursor.getColumnIndex(MediaStore.Audio.AudioColumns.DURATION)));

        double durationInMin = ((double) durationInMs / 1000.0) / 60.0;

        durationInMin = new BigDecimal(Double.toString(durationInMin)).setScale(2, BigDecimal.ROUND_UP).doubleValue();

        duration.setText("" + durationInMin);

        view.setTag(cursor.getString(cursor.getColumnIndex(MediaStore.MediaColumns.DATA)));
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(R.layout.list_item, parent, false);

        bindView(v, context, cursor);

        return v;
    }
}

private View.OnClickListener onButtonClick = new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.play: {
                if (player.isPlaying()) {
                    handler.removeCallbacks(updatePositionRunnable);
                    player.pause();
                    playButton.setImageResource(android.R.drawable.ic_media_play);
                } else {
                    if (isStarted) {
                        player.start();
                        playButton.setImageResource(android.R.drawable.ic_media_pause);

                        updatePosition();
                    } else {
                        startPlay(currentFile);
                    }
                }

                break;
            }
            case R.id.next: {
                int seekto = player.getCurrentPosition() + STEP_VALUE;

                if (seekto > player.getDuration())
                    seekto = player.getDuration();

                player.pause();
                player.seekTo(seekto);
                player.start();

                break;
            }
            case R.id.prev: {
                int seekto = player.getCurrentPosition() - STEP_VALUE;

                if (seekto < 0)
                    seekto = 0;

                player.pause();
                player.seekTo(seekto);
                player.start();

                break;
            }
            case R.id.btNxt: {
            //TO DO
            }
            case R.id.btPrev: {
            //TO DO
            }
        }
    }
};

private MediaPlayer.OnCompletionListener onCompletion = new MediaPlayer.OnCompletionListener() {

    @Override
    public void onCompletion(MediaPlayer mp) {
        stopPlay();
    }
};

private MediaPlayer.OnErrorListener onError = new MediaPlayer.OnErrorListener() {

    @Override
    public boolean onError(MediaPlayer mp, int what, int extra) {

        return false;
    }
};

private SeekBar.OnSeekBarChangeListener seekBarChanged = new SeekBar.OnSeekBarChangeListener() {
    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        isMovingSeekBar = false;
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        isMovingSeekBar = true;
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        if (isMovingSeekBar) {
            player.seekTo(progress);

            Log.i("OnSeekBarChangeListener", "onProgressChanged");
        }
    }
};

Answer 1

你可以看看我下面的方法来播放下一首歌曲。希望对您有所帮助。

public static void nextSong() {
        int numOfSong = songList.size();

        if (!isShuffle) { // Shuffle mode is off
            if (currentPosition < numOfSong - 1) {
                currentPosition++;
                currentSong = songList.get(currentPosition);
                Log.d("my_log", "position = "+currentPosition);
                playBackMusic();
            } else {
                currentPosition = 0;
                currentSong = songList.get(currentPosition);
                Log.d("my_log", "position = "+currentPosition);
                playBackMusic();
            }
        } else { // Shuffle mode is on
            Random rand = new Random();
            currentPosition = rand.nextInt(numOfSong);
            currentSong = songList.get(currentPosition);
            Log.d("my_log", "position = "+currentPosition);
            playBackMusic();
        }
    }

这是播放歌曲的 playBackMusic() 方法:

public static void playBackMusic() {
        try {
            mediaPlayer.release();

            mediaPlayer = new MediaPlayer();
            mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mediaPlayer.setDataSource(currentSong.getPath());
            mediaPlayer.prepare();

            mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    endOfTheSong();
                }
            });

            isPlaying = true;
            mediaPlayer.start();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

方法 endOfTheSong() 处理当前歌曲播放后的操作。

public static void endOfTheSong() {
        if (isRepeat == 1) { // currently repeat one song
            mediaPlayer.seekTo(0);
            mediaPlayer.start();
        } else if (isRepeat == 2) { // currently repeat all songs
            nextSong();
        } else { // currently no repeat

            if (currentPosition != songList.size() - 1) nextSong();

        }
    }