我正在开发一款适用于Android的音乐播放器，而且我遇到了这个问题。
现在我可以播放带有musicservice的歌曲并将其发送到后台，我还会显示当前播放歌曲的通知。
我需要的是从歌曲通知中重新打开主要活动并继续播放歌曲，它实际上启动了所需的活动，但音乐服务被重新创建并停止当前播放的歌曲。
这是我的代码。
MusicService.java
public class MusicService extends Service implements
MediaPlayer.OnPreparedListener,
MediaPlayer.OnErrorListener,
MediaPlayer.OnCompletionListener {
private final IBinder musicBind = new MusicBinder();
//media player
private MediaPlayer player;
//song list
private ArrayList<SongModel> songs;
//current position
private int songPosition;
public MusicService() {
}
public void onCreate() {
//create the service
super.onCreate();
//initialize position
songPosition = 0;
//create player
player = new MediaPlayer();
initMusicPlayer();
}
public void initMusicPlayer() {
//set player properties
player.setWakeMode(getApplicationContext(), PowerManager.PARTIAL_WAKE_LOCK);
player.setAudioStreamType(AudioManager.STREAM_MUSIC);
player.setOnPreparedListener(this);
player.setOnCompletionListener(this);
player.setOnErrorListener(this);
}
public void setList(ArrayList<SongModel> theSongs) {
songs = theSongs;
}
public class MusicBinder extends Binder {
public MusicService getService() {
return MusicService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
return musicBind;
}
@Override
public boolean onUnbind(Intent intent) {
player.stop();
player.release();
return false;
}
public int getPosition() {
return player.getCurrentPosition();
}
public int getCurrenListPosition() {
return songPosition;
}
public int getDuration() {
return player.getDuration();
}
public boolean isPlaying() {
return player.isPlaying();
}
public void pausePlayer() {
player.pause();
}
public void stopPlayer() {
player.stop();
}
public void seekToPosition(int posn) {
player.seekTo(posn);
}
public void start() {
player.start();
}
public void playSong() {
try {
//play a song
player.reset();
SongModel playSong = songs.get(songPosition);
String trackUrl = playSong.getFileUrl();
player.setDataSource(trackUrl);
player.prepareAsync();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onCompletion(MediaPlayer mp) {
if (mp.getCurrentPosition() == 0) {
mp.reset();
}
}
@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
mp.reset();
return false;
}
@Override
public void onPrepared(MediaPlayer mp) {
//start playback
mp.start();
SongModel playingSong = songs.get(songPosition);
Intent intent = new Intent(this, NavDrawerMainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
Notification.Builder builder = new Notification.Builder(this);
builder.setContentIntent(pendingIntent)
.setSmallIcon(R.drawable.ic_action_playing)
.setTicker(playingSong.getTitle())
.setOngoing(true)
.setContentTitle(playingSong.getTitle())
.setContentText(playingSong.getArtistName());
Notification notification = builder.build();
startForeground((int) playingSong.getSongId(), notification);
}
@Override
public void onDestroy() {
stopForeground(true);
}
public void setSong(int songIndex) {
songPosition = songIndex;
}
}
DiscoverSongsFragment.java
public class DiscoverSongsFragment extends Fragment
implements MediaController.MediaPlayerControl {
JazzyGridView songsContainer;
SongsHelper songsHelper;
SongsAdapter songsAdapter;
ArrayList<SongModel> songsArrayList;
ConnectionState connectionState;
Context mContext;
private static View rootView;
SongModel currentSong;
SeekBar nowPlayingSeekBar;
final Handler handler = new Handler();
// this value contains the song duration in milliseconds.
// Look at getDuration() method in MediaPlayer class
int mediaFileLengthInMilliseconds;
View nowPlayingLayout;
boolean nowPlayingLayoutVisible;
TextView nowPlayingTitle;
TextView nowPlayingArtist;
ImageButton nowPlayingCover;
ImageButton nowPlayingStop;
private MusicService musicService;
private Intent playIntent;
private boolean musicBound = false;
private boolean playbackPaused = false;
private int mCurrentTransitionEffect = JazzyHelper.SLIDE_IN;
public static DiscoverSongsFragment newInstance() {
return new DiscoverSongsFragment();
}
public DiscoverSongsFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.fragment_discover_songs, container, false);
mContext = rootView.getContext();
setupViews(rootView);
return rootView;
}
@Override
public void onStart() {
super.onStart();
if (playIntent == null) {
playIntent = new Intent(mContext, MusicService.class);
mContext.bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
mContext.startService(playIntent);
}
}
@Override
public void onResume() {
super.onResume();
if (isPlaying()) {
showNowPlayingLayout();
primarySeekBarProgressUpdater();
}
}
@Override
public void onDestroy() {
mContext.stopService(playIntent);
musicService = null;
super.onDestroy();
}
private void hideNowPlayingLayout() {
nowPlayingLayoutVisible = false;
nowPlayingLayout.setVisibility(View.GONE);
Animation animationFadeIn = AnimationUtils.loadAnimation(mContext, R.anim.fade_out);
nowPlayingLayout.startAnimation(animationFadeIn);
}
private void showNowPlayingLayout() {
nowPlayingLayoutVisible = true;
nowPlayingLayout.setVisibility(View.VISIBLE);
Animation animationFadeIn = AnimationUtils.loadAnimation(mContext, R.anim.fade_in);
nowPlayingLayout.startAnimation(animationFadeIn);
}
private void setupViews(View rootView) {
songsHelper = new SongsHelper();
songsArrayList = new ArrayList<SongModel>();
connectionState = new ConnectionState(mContext);
songsAdapter = new SongsAdapter(mContext, songsArrayList);
nowPlayingLayout = rootView.findViewById(R.id.nowPlayingLayout);
nowPlayingLayout.setVisibility(View.GONE);
nowPlayingLayoutVisible = false;
songsContainer = (JazzyGridView) rootView.findViewById(R.id.songsContainerView);
songsContainer.setTransitionEffect(mCurrentTransitionEffect);
songsContainer.setAdapter(songsAdapter);
songsContainer.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
musicService.setSong(position);
musicService.playSong();
if (playbackPaused) {
playbackPaused = false;
}
currentSong = songsArrayList.get(position);
// gets the song length in milliseconds from URL
mediaFileLengthInMilliseconds = getDuration();
if (currentSong != null) {
nowPlayingTitle.setText(currentSong.getTitle());
nowPlayingArtist.setText(currentSong.getArtistName());
nowPlayingCover.setImageBitmap(currentSong.getCoverArt());
}
primarySeekBarProgressUpdater();
if (!nowPlayingLayoutVisible) {
showNowPlayingLayout();
}
}
});
nowPlayingSeekBar = (SeekBar) rootView.findViewById(R.id.nowPlayingSeekbar);
nowPlayingSeekBar.setMax(99);
nowPlayingTitle = (TextView) rootView.findViewById(R.id.nowPlayingTitle);
nowPlayingArtist = (TextView) rootView.findViewById(R.id.nowPlayingArtist);
nowPlayingStop = (ImageButton) rootView.findViewById(R.id.nowPlayingStop);
nowPlayingStop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isPlaying()) {
currentSong = null;
playbackPaused = false;
musicService.stopPlayer();
mediaFileLengthInMilliseconds = 0;
nowPlayingSeekBar.setProgress(0);
hideNowPlayingLayout();
}
}
});
nowPlayingCover = (ImageButton) rootView.findViewById(R.id.nowPlayingCover);
nowPlayingCover.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
Intent intent = new Intent(mContext, SongDetailsActivity.class);
intent.putExtra("Title", currentSong.getTitle());
intent.putExtra("Artist", currentSong.getArtistName());
intent.putExtra("Album", currentSong.getAlbumName());
intent.putExtra("Genre", currentSong.getGenre());
intent.putExtra("CoverUrl", currentSong.getCoverArtUrl());
startActivity(intent);
} catch (Exception e) {
e.printStackTrace();
}
}
});
getSongs();
hideNowPlayingLayout();
}
private void getSongs() {
if (!connectionState.isConnectedToInternet()) {
}
songsAdapter.clear();
String songsUrl = Constants.getAPI_SONGS_URL();
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(songsUrl, new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray jsonArray) {
if (jsonArray != null) {
for (int i = 0; i < jsonArray.length(); i++) {
try {
JSONObject jsonObject = jsonArray.getJSONObject(i);
SongModel song = songsHelper.getSongFromJson(jsonObject);
songsAdapter.add(song);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError volleyError) {
}
});
AppController.getInstance().addToRequestQueue(jsonArrayRequest);
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
@Override
public void onDetach() {
super.onDetach();
}
/**
* Method which updates the SeekBar primary progress by current song playing position
*/
private void primarySeekBarProgressUpdater() {
nowPlayingSeekBar.setProgress((int) (((float) getCurrentPosition() / getDuration()) * 100));
//if (isPlaying()) {
Runnable runnable = new Runnable() {
public void run() {
primarySeekBarProgressUpdater();
}
};
handler.postDelayed(runnable, 1000);
//}
}
@Override
public void start() {
musicService.start();
}
@Override
public void pause() {
playbackPaused = true;
musicService.pausePlayer();
}
@Override
public int getDuration() {
if (musicService != null && musicBound && musicService.isPlaying()) {
return musicService.getDuration();
}
return 0;
}
@Override
public int getCurrentPosition() {
if (musicService != null && musicBound && musicService.isPlaying()) {
return musicService.getPosition();
}
return 0;
}
public int getCurrentListPosition() {
if (musicService != null && musicBound && musicService.isPlaying()) {
return musicService.getCurrenListPosition();
}
return 0;
}
@Override
public void seekTo(int pos) {
musicService.seekToPosition(pos);
}
@Override
public boolean isPlaying() {
if (musicService != null && musicBound && musicService.isPlaying()) {
return musicService.isPlaying();
}
return false;
}
@Override
public int getBufferPercentage() {
return 0;
}
@Override
public boolean canPause() {
return true;
}
@Override
public boolean canSeekBackward() {
return true;
}
@Override
public boolean canSeekForward() {
return true;
}
@Override
public int getAudioSessionId() {
return 0;
}
//connect to the service
private ServiceConnection musicConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MusicService.MusicBinder binder = (MusicService.MusicBinder) service;
//get service
musicService = binder.getService();
//pass list
musicService.setList(songsArrayList);
musicBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
musicBound = false;
}
};
}
（当浏览抽屉菜单项时，片段也会重新创建）
我希望有人可以帮助我实现这一目标。我不知道如何在重新启动MainActivity时维护状态（顺便说一下，我使用navdrawer来保存片段）
答案 0 :(得分：0)
在通知意图中包含当前播放的歌曲。歌曲改变时更新意图。包括清除顶部的标志和更新通知意图中当前的标志。 :( 抱歉 IDK，如果我的旗帜适合您的情况，但您可以进行更多的研究。
在您创建通知意图的服务中。
// link the notifications to the recorder activity
Intent resultIntent = new Intent(context, KmlReader.class);
resultIntent
.setAction(ServiceLocationRecorder.INTENT_COM_GOSYLVESTER_BESTRIDES_LOCATION_RECORDER);
resultIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent resultPendingIntent = PendingIntent
.getActivity(context, 0, resultIntent,
PendingIntent.FLAG_UPDATE_CURRENT);
mBuilder.setContentIntent(resultPendingIntent);
return mBuilder.build();
}
然后在主onCreate中检查包中当前正在播放的歌曲的名称并显示它。请注意我在使用之前如何检查是否存在捆绑密钥。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
String intentaction = intent.getAction();
// First Run checks
if (savedInstanceState == null) {
// first run init
...
} else {
// get the saved_Instance state
// always get the default when key doesn't exist
// default is null for this example
currentCameraPosition = savedInstanceState
.containsKey(SAVED_INSTANCE_CAMERA_POSITION) ? (CameraPosition) savedInstanceState
.getParcelable(SAVED_INSTANCE_CAMERA_POSITION) : null;
...