这是我关于任何类型音乐播放器的最后一篇帖子，但我真的需要帮助。我正在研究基本的Android音乐播放器应用程序，我无法创建NEXt和PREVIOUS按钮。所以我非常漂亮，如果有人能让我离开那里。我已经尝试了更多关于那个问题的事，谢谢你。我已经创建了这个：
主要应用程序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 ImageButton playButton = null;
private ImageButton previousButton = null;
private ImageButton nextButton = 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);
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE},
1);
selectedFile = (TextView) findViewById(R.id.selectedfile);
seekbar = (SeekBar) findViewById(R.id.seekbar);
playButton = (ImageButton) findViewById(R.id.play);
previousButton = (ImageButton) findViewById(R.id.previous);
nextButton = (ImageButton) findViewById(R.id.next);
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.listitem, cursor);
setListAdapter(mediaAdapter);
playButton.setOnClickListener(onButtonClick);
nextButton.setOnClickListener(onButtonClick);
previousButton.setOnClickListener(onButtonClick);
}
}
@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) {
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.setSecondaryProgressTintMode(player.getCurrentPosition());
handler.postDelayed(updatePositionRunnable, UPDATE_FREQUENCY);
}
private class MediaCursorAdapter extends SimpleCursorAdapter{
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)));
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.listitem, 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.previous: {
int seekto = player.getCurrentPosition() - STEP_VALUE;
if (seekto < player.getDuration())
seekto = player.getDuration();
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 onStopTrackingTouch(SeekBar seekBar) {
isMovingseekBar = false;
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fomUser) {
if (isMovingseekBar) {
player.seekTo(progress);
Log.i("OnSeekBarChangeListener", "onProgressChange");
}
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
isMovingseekBar = true;
}
};
}
我已经用NEXT和PREVIOUS按钮进行了切换，我试图让它们工作但是我最终得到的歌曲不是NEXT或PREVIOUS。