以下是我的音乐播放器的服务类,从未调用实现的onPrepared()方法,因此我必须使用setOnPreparedListener来完成所有工作。 我想从未实现的部分执行它。
public class MusicService extends Service implements MediaPlayer.OnPreparedListener,
MediaPlayer.OnErrorListener,MediaPlayer.OnCompletionListener {
//media player
private MediaPlayer player;
//song list
private ArrayList<Song> songs;
//current position
private int songPosn;
private String songTitle="";
private static final int NOTIFY_ID=1;
private final IBinder musicBind = new MusicBinder();
@Override
public IBinder onBind(Intent intent) {
return musicBind;
}
public boolean onUnbind(Intent intent){
player.stop();
player.release();
return false;
}
@Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
//initialize position
songPosn = 0;
//create player
player = new MediaPlayer();
}
@Override
public void onCompletion(MediaPlayer mp) {
// TODO Auto-generated method stub
}
@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
// TODO Auto-generated method stub
return false;
}
//this is never being called and instead of this the one in setOnPreparedListener is called
@Override
public void onPrepared(MediaPlayer mp) {
// TODO Auto-generated method stub
//start music
mp.start();
Intent notIntent = new Intent(this, MainActivity.class);
notIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendInt = PendingIntent.getActivity(this, 0, notIntent, PendingIntent.FLAG_UPDATE_CURRENT);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setContentIntent(pendInt)
.setSmallIcon(R.drawable.play)
.setTicker(songTitle)
.setOngoing(true)
.setContentText("Playing")
.setContentText(songTitle);
Notification not = builder.build();
startForeground(NOTIFY_ID, not);
}
public void initMusicPlayer(){
//set player properties
player.setWakeMode(getApplicationContext(), PowerManager.PARTIAL_WAKE_LOCK);
player.setAudioStreamType(AudioManager.STREAM_MUSIC);
}
public void setSong(int songIndex){
songPosn=songIndex;
}
public void setList(ArrayList<Song> theSongs){
songs = theSongs;
}
public void playSong(){
//play a cool song
player.reset();
//get song
Song playSong = songs.get(songPosn);
songTitle = playSong.getTitle();
//get ID
long currSong = playSong.getId();
//set path to sdcard or squaremash server
Uri trackUri = ContentUris.withAppendedId(android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, currSong);
try {
player.setDataSource(getApplicationContext(), trackUri);
} catch (Exception e) {
Log.e("Music service","Error: setting data source",e); }
player.prepareAsync();
//this one is called, If I remove this, the above onPrepared method isnt called
player.setOnPreparedListener(new OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
// TODO Auto-generated method stub
mp.start();
}
});
}
public void go(){
player.start();
}
//previous song
public void playPrev() {
songPosn--;
if(songPosn<0)
songPosn=songs.size()-1;
playSong();
}
//next song
public void playNext() {
songPosn++;
if(songPosn>=songs.size())
songPosn=0;
playSong();
}
}
答案 0 :(得分:3)
这不是Java的工作方式。
您正在扩展Service
个对象。该对象的生命周期中没有任何内容触发对onPrepared()
的调用。触发该呼叫的是您的player
成员:
private MediaPlayer player;
要实现这一点,即player
触发对onPrepared()
的调用,您需要将其指向实现onPrepared()
的对象。该对象是您的MusicService
对象,因此您需要调用:
player.setOnPreparedListener(this);
答案 1 :(得分:1)
您没有设置正确的OnPreparedListener。
在onCreate()
创建播放器时,您应该在那里设置监听器:
player = new MediaPlayer();
player.setOnPreparedListener(this)
然后移除另一个,否则它将覆盖第一个。
当你实现一个接口时,它只是在类上设置一个契约:“这个类具有这些特殊的方法,随时可以调用它们”。 MediaPlayer
需要知道要使用哪个 OnPreparedListener
(MediaPlayer.setOnPreparedListener
),否则它将无法执行任何操作。