我遇到以下代码的问题。我在MediaController上调用了setPrevNextListener，并为Prev和Next定义了两个onClickListener。当我单击下一个按钮而不是前进一个轨道时，我前进两个轨道。这似乎是由于onCompletion被某种方式调用的事实。 MediaPlayer.reset（）是否会调用onCompletion？我已经包含了logcat输出和我的代码。如果我做错了，请告诉我。提前谢谢。
logcat的：
02-24 00:36:34.826: D/MP(6675): Next Button Clicked, index was: 0
02-24 00:36:34.837: D/MP(6675): About to call Reset()
02-24 00:36:34.906: D/MP(6675): Inside setUpPlayer
02-24 00:36:34.917: D/MP(6675): Called setDataSource with index: 1
02-24 00:36:34.917: D/MP(6675): Leaving setUpPlayer
02-24 00:36:34.917: D/MP(6675): About to call prepareAsync()
02-24 00:36:34.937: D/MP(6675): Leaving next button
02-24 00:36:35.226: E/MediaPlayer(6675): Attempt to call getDuration without a valid mediaplayer
02-24 00:36:35.226: E/MediaPlayer(6675): error (-38, 0)
02-24 00:36:35.276: E/MediaPlayer(6675): Error (-38,0)
02-24 00:36:35.287: D/MP(6675): Inside onCompletion
02-24 00:36:35.337: D/MP(6675): About to call Reset()
02-24 00:36:35.347: D/MP(6675): Inside setUpPlayer
02-24 00:36:35.356: D/MP(6675): Called setDataSource with index: 2
02-24 00:36:35.356: D/MP(6675): Leaving setUpPlayer
02-24 00:36:35.356: D/MP(6675): About to call prepareAsync()
02-24 00:36:35.377: D/MP(6675): Leaving onCompletion
02-24 00:36:36.517: D/MP(6675): Inside onPrepared, index is: 2
02-24 00:36:36.577: D/MP(6675): Leaving onPrepared
代码：
public class MusicPlayerActivity extends Activity implements OnPreparedListener, OnCompletionListener, MediaController.MediaPlayerControl {
private MediaPlayer mp;
private MediaController mc;
private SonarDatabase db;
private SubsonicAPIConnector sonic;
ArrayList<String> songs;
int index = 0;
private Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.music_player);
// Get params from intent
Intent i = getIntent();
String albumId = i.getStringExtra("albumId");
String artistId = i.getStringExtra("artistId");
String albumName = i.getStringExtra("albumName");
String songName = i.getStringExtra("songName");
String songId = i.getStringExtra("songId");
String coverArt = "al-"+albumId+".jpeg";
String duration = i.getStringExtra("duration");
Log.d("MP", "results: albumName:" + albumName + ", songName: " + songName + ", songId: "
+ songId + ", duration: " + duration + ", coverArt: " + coverArt + ", artistId: "
+ artistId + ", albumId: " + albumId);
db = new SonarDatabase(getApplicationContext());
sonic = new SubsonicAPIConnector(db.getURL(), db.getUsername(), db.getPassword());
String artistName = db.getArtistNameById(artistId);
setTitle("Now Playing");
songs = db.getSongListForAlbum(albumId);
index = songs.indexOf(songId);
Log.d("MP", "songid: " + songId + ", index: " + index);
// Update text views with song information
TextView txtArtist = (TextView) findViewById(R.id.txtArtistName);
txtArtist.setText(artistName);
TextView txtAlbum = (TextView) findViewById(R.id.txtAlbumName);
txtAlbum.setText(albumName);
TextView txtSong = (TextView) findViewById(R.id.txtSongName);
txtSong.setText(songName);
// Show the album art
File img = new File(this.getFilesDir()+"/covers/"+coverArt);
if(img.exists()) {
Log.d("MP", "Found image at: " + img.toString());
ImageView imgView = (ImageView) findViewById(R.id.cover_art);
imgView.setImageBitmap(BitmapFactory.decodeFile(img.getPath()));
} else {
Log.d("MP", "Couldn't find image: " + img.toString());
}
// Create the media player and controller
mp = new MediaPlayer();
mp.setOnPreparedListener(this);
mp.setOnCompletionListener(this);
mc = new NonHidingMediaController(this);
mc.setPrevNextListeners(new View.OnClickListener() {
@Override
public void onClick(View v) {
// next button clicked
Log.d("MP", "Next Button Clicked, index was: " + index);
playNextTrack();
Log.d("MP", "Leaving next button");
}
}, new View.OnClickListener() {
@Override
public void onClick(View v) {
// previous button clicked
Log.d("MP", "Previous button clicked, index was: " + index);
if(mp.isPlaying() && mp.getCurrentPosition() < 2000 && index != 0) {
Log.d("MP", "Start the prior song.");
playPreviousTrack();
} else {
Log.d("MP", "Restart this song.");
restartCurrentTrack();
}
Log.d("MP", "Leaving previous button");
}
});
mc.setMediaPlayer(this);
setUpPlayer();
Log.d("MP", "About to call prepareAsync()");
mp.prepareAsync();
}
@Override
public void onCompletion(MediaPlayer mp) {
Log.d("MP", "Inside onCompletion");
//TODO add code for scrobbling here.
playNextTrack();
Log.d("MP", "Leaving onCompletion");
}
private void playNextTrack() {
index++;
TextView txtSong = (TextView) findViewById(R.id.txtSongName);
txtSong.setText(db.getSongNameById(songs.get(index)));
Log.d("MP", "About to call Reset()");
mp.reset();
setUpPlayer();
Log.d("MP", "About to call prepareAsync()");
mp.prepareAsync();
}
private void playPreviousTrack() {
index--;
TextView txtSong = (TextView) findViewById(R.id.txtSongName);
txtSong.setText(db.getSongNameById(songs.get(index)));
Log.d("MP", "About to call Reset()");
mp.reset();
setUpPlayer();
Log.d("MP", "About to call prepareAsync()");
mp.prepareAsync();
}
private void restartCurrentTrack() {
mp.seekTo(0);
}
public void onPrepared(MediaPlayer mp) {
Log.d("MP", "Inside onPrepared, index is: " + index);
mc.setMediaPlayer(this);
mc.setAnchorView(findViewById(R.id.music_player_view));
mp.start();
handler.post(new Runnable() {
public void run() {
mc.setEnabled(true);
mc.show();
}
});
Log.d("MP", "Leaving onPrepared");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_music_player, menu);
return true;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.d("MP", "OnTouchEvent called");
mc.show();
return false;
}
private void setUpPlayer() {
Log.d("MP", "Inside setUpPlayer");
mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
try {
mp.setDataSource(sonic.streamString("&id=" + songs.get(index)));
Log.d("MP", "Called setDataSource with index: " + index);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Log.d("MP", "Leaving setUpPlayer");
}
@Override
protected void onStop() {
super.onStop();
mc.hide();
mp.stop();
mp.release();
}
public void start() {
mp.start();
}
public void pause() {
mp.pause();
}
public int getDuration() {
return mp.getDuration();
}
public int getCurrentPosition() {
return mp.getCurrentPosition();
}
public void seekTo(int i) {
mp.seekTo(i);
}
public boolean isPlaying() {
return mp.isPlaying();
}
public int getBufferPercentage() {
return 0;
}
public boolean canPause() {
return true;
}
public boolean canSeekBackward() {
return true;
}
public boolean canSeekForward() {
return true;
}
public class NonHidingMediaController extends MediaController {
public NonHidingMediaController(Context context, AttributeSet attrs) {
super(context, attrs);
}
public NonHidingMediaController(Context context, boolean useFastForward) {
super(context, useFastForward);
}
public NonHidingMediaController(Context context) {
super(context);
}
@Override
public void show(int timeout) {
super.show(0);
}
}
}
答案 0 :(得分：22)
我对android源码进行了一些挖掘，发现任何未处理的错误都会导致MediaPlayer调用onCompletion处理程序。在这种情况下，您似乎在空闲，初始化或错误状态下调用getDuration。可以从媒体控制器内部进行。我建议在任何调用getDuration的地方之前添加一些Log.d（），以查看导致问题的调用的位置。
答案 1 :(得分：11)
添加MediaPlayer.OnErrorLisener并从覆盖方法
返回truemediaPlayer.setOnErrorListener(new MediaPlayer.OnErrorListener() {
@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
return true;
}
});