Question

我引用这个tut http://code.tutsplus.com/tutorials/create-a-music-player-on-android-user-controls--mobile-22787创建app来播放mp3文件。但是当我按下后退按钮时，播放停止。当然，在onDestroy（）方法上，我没有像这样实施停止服务。

感谢您的帮助。

public class MainActivity extends Activity {

    //song list variables
    private ArrayList<Song> songList;
    private ListView songView;

    //service
    private MusicService musicSrv;
    private Intent playIntent;
    //binding
    private boolean musicBound=false;

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

        //retrieve list view
        songView = (ListView)findViewById(R.id.song_list);
        //instantiate list
        songList = new ArrayList<Song>();
        //get songs from device
        getSongList();
        //sort alphabetically by title
        Collections.sort(songList, new Comparator<Song>(){
            public int compare(Song a, Song b){
                return a.getTitle().compareTo(b.getTitle());
            }
        });
        //create and set adapter
        SongAdapter songAdt = new SongAdapter(this, songList);
        songView.setAdapter(songAdt);
    }

    //connect to the service
    private ServiceConnection musicConnection = new ServiceConnection(){

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            MusicBinder binder = (MusicBinder)service;
            //get service
            musicSrv = binder.getService();
            //pass list
            musicSrv.setList(songList);
            musicBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            musicBound = false;
        }
    };

    //start and bind the service when the activity starts
    @Override
    protected void onStart() {
        super.onStart();
        if(playIntent==null){
            playIntent = new Intent(this, MusicService.class);
            bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
            startService(playIntent);
        }
    }

    //user song select
    public void songPicked(View view){
        musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
        musicSrv.playSong();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        //menu item selected
        switch (item.getItemId()) {
        case R.id.action_shuffle:
            //shuffle
            break;
        case R.id.action_end:
            stopService(playIntent);
            musicSrv=null;
            System.exit(0);
            break;
        }
        return super.onOptionsItemSelected(item);
    }

    //method to retrieve song info from device
    public void getSongList(){
        //query external audio
        ContentResolver musicResolver = getContentResolver();
        Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
        //iterate over results if valid
        if(musicCursor!=null && musicCursor.moveToFirst()){
            //get columns
            int titleColumn = musicCursor.getColumnIndex
                    (android.provider.MediaStore.Audio.Media.TITLE);
            int idColumn = musicCursor.getColumnIndex
                    (android.provider.MediaStore.Audio.Media._ID);
            int artistColumn = musicCursor.getColumnIndex
                    (android.provider.MediaStore.Audio.Media.ARTIST);
            //add songs to list
            do {
                long thisId = musicCursor.getLong(idColumn);
                String thisTitle = musicCursor.getString(titleColumn);
                String thisArtist = musicCursor.getString(artistColumn);
                songList.add(new Song(thisId, thisTitle, thisArtist));
            } 
            while (musicCursor.moveToNext());
        }
    }

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

}

音乐服务

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;
    //binder
    private final IBinder musicBind = new MusicBinder();

    public void onCreate(){
        //create the service
        super.onCreate();
        //initialize position
        songPosn=0;
        //create player
        player = new MediaPlayer();
        //initialize
        initMusicPlayer();
    }

    public void initMusicPlayer(){
        //set player properties
        player.setWakeMode(getApplicationContext(), 
                PowerManager.PARTIAL_WAKE_LOCK);
        player.setAudioStreamType(AudioManager.STREAM_MUSIC);
        //set listeners
        player.setOnPreparedListener(this);
        player.setOnCompletionListener(this);
        player.setOnErrorListener(this);
    }

    //pass song list
    public void setList(ArrayList<Song> theSongs){
        songs=theSongs;
    }

    //binder
    public class MusicBinder extends Binder {
        MusicService getService() { 
            return MusicService.this;
        }
    }

    //activity will bind to service
    @Override
    public IBinder onBind(Intent intent) {
        return musicBind;
    }

    //release resources when unbind
    @Override
    public boolean onUnbind(Intent intent){
        player.stop();
        player.release();
        return false;
    }

    //play a song
    public void playSong(){
        //play
        player.reset();
        //get song
        Song playSong = songs.get(songPosn);
        //get id
        long currSong = playSong.getID();
        //set uri
        Uri trackUri = ContentUris.withAppendedId(
                android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                currSong);
        //set the data source
        try{ 
            player.setDataSource(getApplicationContext(), trackUri);
        }
        catch(Exception e){
            Log.e("MUSIC SERVICE", "Error setting data source", e);
        }
        player.prepareAsync(); 
    }

    //set the song
    public void setSong(int songIndex){
        songPosn=songIndex; 
    }

    @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;
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        //start playback
        mp.start();
    }

}

Answer 1

试试这个：

在onStartCommand中，在你的代码播放mps之后，return START_STICKY

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    // play mp3 code here
    return START_STICKY;
}

代码更新后：

你将服务限制在与你的活动相关的游戏意图上，所以当你破坏你的活动时，eq。按回来，该服务将被取消简单的解决方案是不将服务绑定到您的活动，并将您的服务代码放在onBind的{{1}}部分中，并将其作为onStartCommand返回，这样您的服务将继续运行在背景中，直到你调用START_STICKY，这可能应该在音乐结束时调用

Answer 2

我意识到因为我在MainActivity中创建了MusicSrv，当Activity的销毁MusicSrv消失了。但是如果我不在MainActivity中创建MusicSrv，我该如何设置列表歌曲或将MainActivity放入MusicSrv来更新UI。

Answer 3

上帝说，因为愚蠢的代码片段

@Override
public boolean onUnbind(Intent intent){
    player.stop();
    player.release();
    return false;
}

Answer 4

startforeground（）的好例子： https://github.com/commonsguy/cw-android/tree/master/Notifications/FakePlayer

与服务互动的好例子： http://code.tutsplus.com/tutorials/create-a-music-player-on-android-user-controls--mobile-22787

使用Android服务播放媒体

4 个答案: