我正在开发一个带音频播放器的应用程序。我想添加下一首歌曲播放按钮和上一首歌曲播放按钮。以下是我的代码，但在此代码中，我想添加下一个曲目播放和上一个曲目播放按钮。帮助我!!
//MainActivity.java
public class MainActivity extends ListActivity {
private static final int UPDATE_FREQUENCY = 500;
private static final int STEP_VALUE = 4000;
private TextView selectedfile = null;
private SeekBar seekBar = null;
private MediaPlayer player = null;
private ImageButton prev = null;
private ImageButton play = null;
private ImageButton next = null;
private MediaCursorAdapter adapter = null;
private boolean isStarted = true;
private String currentFile = "";
private boolean isMovingSeekBar = false;
private final Handler handler = new Handler();
private final Runnable updatePositinRunnable = new Runnable() {
@Override
public void run() {
updatePosition();
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
selectedfile = (TextView) findViewById(R.id.selecteditem);
seekBar = (SeekBar) findViewById(R.id.seekBar);
prev = (ImageButton) findViewById(R.id.previous);
play = (ImageButton) findViewById(R.id.play);
next = (ImageButton) findViewById(R.id.next);
player = new MediaPlayer();
player.setOnCompletionListener(onCompletion);
player.setOnErrorListener(onError);
seekBar.setOnSeekBarChangeListener(seekBarChanged);
Cursor cursor = getContentResolver().query(MediaStore.Audio.Media.
INTERNAL_CONTENT_URI, null, null, null, null);
if (null != cursor) {
cursor.moveToFirst();
adapter = new MediaCursorAdapter(this, R.layout.item, cursor);
setListAdapter(adapter);
prev.setOnClickListener(OnButtonClick);
play.setOnClickListener(OnButtonClick);
next.setOnClickListener(OnButtonClick);
}
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
currentFile = (String) v.getTag();
startPlay(currentFile);
}
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());
play.setImageResource(android.R.drawable.ic_media_pause);
updatePosition();
isStarted = true;
}
private void stopPlay() {
player.stop();
player.reset();
play.setImageResource(android.R.drawable.ic_media_play);
handler.removeCallbacks(updatePositinRunnable);
seekBar.setProgress(0);
isStarted = false;
}
@Override
protected void onDestroy() {
super.onDestroy();
handler.removeCallbacks(updatePositinRunnable);
player.stop();
player.reset();
player.release();
player = null;
}
private void updatePosition() {
handler.removeCallbacks(updatePositinRunnable);
seekBar.setProgress(player.getCurrentPosition());
handler.postDelayed(updatePositinRunnable, UPDATE_FREQUENCY);
}
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(updatePositinRunnable);
player.pause();
play.setImageResource(android.R.drawable.ic_media_play);
} else {
if (isStarted) {
player.start();
play.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.previous: {
int seekto = player.getCurrentPosition() - STEP_VALUE;
if (seekto < 0)
seekto = 0;
player.pause();
player.seekTo(seekto);
player.start();
break;
}
}
}
};
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 onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if (isMovingSeekBar) {
player.seekTo(progress);
Log.i("OnSeekBarChangeListener", "OnProgressChanged");
}
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
isMovingSeekBar = true;
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
isMovingSeekBar = false;
}
};
}
//MediaCursorAdapter.java
public 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.item, parent, false);
bindView(v, context, cursor);
return v;
}
}