Android-在活动中恢复服务并在销毁时销毁它们

Question

我目前有一个 Activty，在创建时会启动并与 service 绑定。此服务有一个mediaplayer。我想做的是，如果活动恢复，则服务继续播放，等等。当活动被销毁时，它应该<代码>停止服务。到目前为止，我可以让服务在重新激活活动时继续播放，也可以让服务在创建新活动时停止，但不能同时使用两者。有什么建议或想法吗？谢谢。代码如下：

活动类别：

public class DUBAudioActivity extends Activity{

    private static final String TAG = DUBAudioActivity.class.getSimpleName();

    Button playPauseButtonDUB;
    Intent playbackServiceIntentDUB;


    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sdrplaylist_dubstep);

        playPauseButtonDUB = (Button)findViewById(R.id.playpausebuttonDUB);

        playbackServiceIntentDUB = new Intent(this, DUBAudioService.class);
        Log.d(TAG, "created intent");

        startService(playbackServiceIntentDUB);

        Log.d(TAG, "bound service");
        //
        //set button text
         playPauseButtonDUB.setText("Pause");
         //set button tag
        playPauseButtonDUB.setTag(1);



        playPauseButtonDUB.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View v) {
                //set the tag stuff
                final int status = (Integer) v.getTag();
                //create if statement for the button to do play and pause
                if(status==1){
                    playPauseButtonDUB.setText("Play");
                    v.setTag(0);
                    Log.d(TAG, "set tag to 0");
                    baServiceDUB.pauseSong();
                    Log.d(TAG, "pause song");   
                }else{
                    playPauseButtonDUB.setText("Pause");
                    v.setTag(1);
                    Log.d(TAG, "set tag to 1");
                    baServiceDUB.playSong();
                    Log.d(TAG, "song play'd");
                }

            }

        });
    //
    }
    private DUBAudioService baServiceDUB;

    private ServiceConnection serviceConnectionDUB = new ServiceConnection(){
        public void onServiceConnected(ComponentName className, IBinder baBinder) {
            baServiceDUB =
            ((DUBAudioService.DUBBackgroundAudioServiceBinder)baBinder).getService();
        }

        public void onServiceDisconnected(ComponentName className){
            baServiceDUB = null;
        }
//
    };

    void doBindService(){
        getApplicationContext().bindService(playbackServiceIntentDUB, serviceConnectionDUB,
                Context.BIND_AUTO_CREATE);
        Log.d(TAG, "do bind service");

    }

    @Override
    public void onResume() {
        getApplicationContext().bindService(playbackServiceIntentDUB, serviceConnectionDUB,
                Context.BIND_AUTO_CREATE);
            Log.d(TAG, "on resume + re-bound service");
        super.onResume();
    }

    @Override
    public void onDestroy(){
        stopService(playbackServiceIntentDUB);
        getApplicationContext().unbindService(serviceConnectionDUB);

        Log.d(TAG, "destroy'd + unbind service");
        //finish();
        super.onDestroy();
    }

}

服务类别：

public class DUBAudioService extends Service implements OnPreparedListener, OnCompletionListener{

Toast loadingMessage;

private static final String TAG = DUBAudioService.class.getSimpleName();

    public boolean isRunning;

    //to keep track of the playlist item
    Vector<PlaylistFile> playlistItems;

    MediaPlayer mediaPlayer;

    String baseURL = "";

    //keep track of which item from the vector we are on
    int currentPlaylistltemNumber = 0;

    public class DUBBackgroundAudioServiceBinder extends Binder {
        DUBAudioService getService() {
        return DUBAudioService.this;
        }
    }

    private final IBinder basBinderDUB = new DUBBackgroundAudioServiceBinder();



    @Override
    public IBinder onBind(Intent intent) {
        return basBinderDUB;
    }

    @Override
    public void onCreate() {
        Log.v("PLAYERSERVICE", "onCreate");
        mediaPlayer = new MediaPlayer();
        new MusicAsync().execute();
            Log.d(TAG, "execute'd async");
        mediaPlayer.setOnPreparedListener(this);
            Log.d(TAG, "set on prepared listener");
        mediaPlayer.setOnCompletionListener(this);
            Log.d(TAG, "set on completion listener");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        //if (!mediaPlayer.isPlaying()) {
        //  mediaPlayer.start();
        //}
        return START_STICKY;
    }

    class MusicAsync extends AsyncTask<Void,Void,Void>{
        @Override
        protected void onPreExecute(){
        }
        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub

            //create empty vector 
            playlistItems = new Vector<PlaylistFile>();

            //HTTP client library
            HttpClient httpClient = new DefaultHttpClient();
            HttpGet getRequest = new HttpGet ("http://dl.dropbox.com/u/24535120/m3u%20playlist/DubstepPlaylist.m3u"); //i think you could add the m3u thing in here 

            Log.v("URI",getRequest.getURI().toString());

            try {
            HttpResponse httpResponse = httpClient.execute(getRequest);
            if (httpResponse.getStatusLine().getStatusCode() != HttpStatus.SC_OK) {
            // ERROR MESSAGE
            Log.v("HTTP ERROR",httpResponse.getStatusLine().getReasonPhrase());
            }
            else {
                InputStream inputStream = httpResponse.getEntity().getContent(); 
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

                String line;
                while ((line = bufferedReader.readLine()) != null) { 
                    Log.v("PLAYLISTLINE","ORIG: " + line);

                    if (line.startsWith("#")) {
                        //Metadata
                        //Could do more with this but not fo now
                    } else if (line.length() > 0) {
                        String filePath = "";
                            if (line.startsWith("http://")) {
                            // Assume its a full URL 
                                filePath = line;
                            } else {
                            //Assume it’s relative
                            filePath = getRequest.getURI().resolve(line).toString();
                            }

                            PlaylistFile playlistFile = new PlaylistFile(filePath);
                            playlistItems.add (playlistFile);
                            }
                            }
                            inputStream.close();
                            }
                            } catch (ClientProtocolException e) { 
                                e.printStackTrace();
                            } catch (IOException e) {
                            e. printStackTrace();
                            }


                            currentPlaylistltemNumber = 0;
                            if (playlistItems.size() > 0)
                            {
                            String path = ((PlaylistFile)playlistItems.get(currentPlaylistltemNumber)).getFilePath();
                            try {
                                mediaPlayer.setDataSource(path);

                            mediaPlayer.prepareAsync();}
                            catch (IllegalArgumentException e) 
                            { e.printStackTrace();
                            }catch (IllegalStateException e) { 
                                e.printStackTrace();
                            }catch (IOException e) {
                            e.printStackTrace();}
                            }



            return null;
        }
        //
        protected void onPostExecute(Void result){
            //playButton. setEnabled (false);
        }
    }



    @Override
    public void onStart(Intent intent, int startId) {
        // TODO Auto-generated method stub

        super.onStart(intent, startId);
    }

    public void onDestroy() {
        if (mediaPlayer.isPlaying()) {
            mediaPlayer.stop();
            Log.d(TAG, "music stopp'd");
        }
        //mediaPlayer.release();
        Log.d(TAG, "onDestroy");
    }

    @Override
    public void onPrepared(MediaPlayer mediaPlayer) {
        // TODO Auto-generated method stub\
        Log.d(TAG, "music is prepared and will start");
        mediaPlayer.start();
    }

    public void onCompletion(MediaPlayer _mediaPlayer) {
        Log.d(TAG, "Song completed, next song");
        mediaPlayer.stop();
        mediaPlayer.reset();
            if (playlistItems.size() > currentPlaylistltemNumber + 1) { 
                currentPlaylistltemNumber++;
            String path =
                ((PlaylistFile)playlistItems.get(currentPlaylistltemNumber)).getFilePath();
                try {
                    mediaPlayer.setDataSource(path);
                    mediaPlayer.prepareAsync();
                } catch (IllegalArgumentException e) { 
                    e. printStackTrace();
                } catch (IllegalStateException e) { 
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }   
    }

    class PlaylistFile {
        String filePath;
            public PlaylistFile(String _filePath) {
                filePath = _filePath;
            }
            public void setFilePath(String _filePath) {
                filePath = _filePath;
            }
            public String getFilePath() {
                return filePath;
            }
        }


    public void playSong(){
        Log.d(TAG, "start'd");
        mediaPlayer.start();
    }

    public void pauseSong(){
        Log.d(TAG, "pause'd");
        mediaPlayer.pause();
    }



}

Answer 1

我想说你很幸运它停止了——当你的 Activity 进入后台时，只有 onPause() 保证被调用。唯一一次调用 onDestroy() 是在系统决定回收您的应用正在使用的内存时。

唯一有保证的生命周期调用是：

• onCreate() 仅当应用从头开始；
• onResume() 每次运行，无论是暂停还是第一次创建；
• 每次系统将您的应用程序移动到后台时，onPause()。