找不到歌曲，同时从播放列表中获得音频ID

Question

我想根据特定的播放列表获取歌曲。我获取所有歌曲的音频编号，但没有得到任何其他信息，如标题，艺术家，专辑等。我也试过 this这与我的问题是一样的。
这是我怎么添加歌曲到播放列表：

public static void addToPlaylist(ContentResolver resolver, long audioId, int playlistId) { 
    String[] cols = new String[] { 
      "count(*)" 
    }; 
    Uri uri = MediaStore.Audio.Playlists.Members.getContentUri("external", playlistId); 
    Cursor cur = resolver.query(uri, cols, null, null, null); 
    cur.moveToFirst(); 
    final int base = cur.getInt(0); 
    cur.close(); 
    ContentValues values = new ContentValues(); 
    values.put(MediaStore.Audio.Playlists.Members.PLAY_ORDER, Integer.valueOf(base +(int) audioId)); 
    values.put(MediaStore.Audio.Playlists.Members.AUDIO_ID, audioId); 
    Uri u =resolver.insert(uri, values); 
    Log.d("ItemFragment", "Added Playlist Item: " + u + " for AUDIO_ID " + audioId+" and PLAYLIST_ID = "+playlistId); 

} 

，然后我检索特定播放列表的歌曲是这样的：

public ArrayList<AudioFile> getSongListFromPlayList() { 
    ArrayList<AudioFile> audioFiles = new ArrayList<>(); 
    String[] proj = { MediaStore.Audio.Playlists.Members.AUDIO_ID}; 
    Cursor musicCursor = musicResolver.query(MediaStore.Audio.Playlists.Members.getContentUri("external",id) 
      , proj, null, null, null); 
    int x = 0; 
    Log.d(TAG,"cursor count : "+musicCursor.getCount()); 
    if ((musicCursor != null) && (musicCursor.moveToFirst())) { 
     do { 
      long a_id = musicCursor.getLong(musicCursor.getColumnIndex(MediaStore.Audio.Playlists.Members.AUDIO_ID)); 
      Uri mediaContentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI; 
      String[] projection = new String[]{MediaStore.Audio.Media._ID, MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.ALBUM, 
        MediaStore.Audio.Media.DURATION, MediaStore.Audio.Media.DATA, MediaStore.Audio.Media.ALBUM_ID}; 
      String selection = MediaStore.Audio.Media._ID + "=?"; 
      String[] selectionArgs = new String[]{"" + a_id}; //This is the id you are looking for 

      Cursor mediaCursor = musicResolver.query(mediaContentUri, projection, selection, selectionArgs, null); 
      Log.d(TAG,"second cursor count : "+mediaCursor.getCount()); 
      if (mediaCursor.getCount() > 0) { 
       mediaCursor.moveToPosition(0); 
       String title = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.TITLE)); 
       String album = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.ALBUM)); 
       String artist = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)); 
       String data = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.DATA)); 
       String duration = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.DURATION)); 
       long id = mediaCursor.getLong(mediaCursor.getColumnIndex(MediaStore.Audio.Media._ID)); 

       audioFiles.add(new AudioFile(id,title,artist,data,duration,x)); 
       x++; 
      } 
     }while (musicCursor.moveToNext()); 
    } 
    Log.d(TAG,"size : "+audioFiles.size()); 
    return audioFiles; 
} 

和调试时我得到日志：

D/SecondActivity：游标数：11
D/SecondActivity：第二游标数：1
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
d/SecondActivity：第二光标计数：0
D/SecondActivity：第二个游标数：0
D/SecondActivity：size：1

请大家帮忙。

Answer 1

您需要枚举光标并向前移动，直到达到最终。一旦你有你的音乐光标，使用这样的东西循环它

   if(musicCursor!= null && musicCursor.moveToFirst()){ 
      for (musicCursor.moveToFirst(); !musicCursor.isAfterLast(); musicCursor.moveToNext()) { 
     // do your stuff here, as you cycle through your musicCursor you will read the next audio_id which then gets the relevant data 
      } 
     } 

for循环将枚举游标。移除moveto位置， 将uri带到循环之外。如果你在这个类中有几个方法，把它放在最前面，这样它就可以用于所有的方法，但你只需定义一次。定义投影只需要在for循环之外进行一次。 我已编辑你的代码有点

public ArrayList<AudioFile> getSongListFromPlayList() { 
ArrayList<AudioFile> audioFiles = new ArrayList<>(); 
String[] proj = { MediaStore.Audio.Playlists.Members.AUDIO_ID}; 
Cursor musicCursor = musicResolver.query(MediaStore.Audio.Playlists.Members.getContentUri("external",id) 
     , proj, null, null, null); 

     String[] projection = new String[]{MediaStore.Audio.Media._ID, MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.ALBUM, 
       MediaStore.Audio.Media.DURATION, MediaStore.Audio.Media.DATA, MediaStore.Audio.Media.ALBUM_ID}; 
     String selection = MediaStore.Audio.Media._ID + "=?"; 
if ((musicCursor != null) && (musicCursor.moveToFirst())) { 
     for (musicCursor.moveToFirst(); !musicCursor.isAfterLast(); musicCursor.moveToNext()) { 
     long a_id = musicCursor.getLong(musicCursor.getColumnIndex(MediaStore.Audio.Playlists.Members.AUDIO_ID)); 

     String[] selectionArgs = new String[]{"" + a_id}; //This is the id you are looking for 
     Cursor mediaCursor = musicResolver.query(mediaContentUri, projection, selection, selectionArgs, null); 
      String title = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.TITLE)); 
      String album = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.ALBUM)); 
      String artist = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)); 
      String data = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.DATA)); 
      String duration = mediaCursor.getString(mediaCursor.getColumnIndex(MediaStore.Audio.Media.DURATION)); 
      long id = mediaCursor.getLong(mediaCursor.getColumnIndex(MediaStore.Audio.Media._ID)); 
      audioFiles.add(new AudioFile(id,title,artist,data,duration,x)); 

    } 
     } 


Log.d(TAG,"size : "+audioFiles.size()); 
return audioFiles;