android - MediaStore.Audio.Playlists.Members.getContentUri 的 String 'volumeName' 参数指的是什么？

Question

我想查询给定播放列表的成员。我有正确的播放列表 ID，并想使用 managedQuery() 查看有问题的播放列表成员。

我的是这样的:

private String [] columns = { 
     MediaStore.Audio.Playlists.Members.PLAYLIST_ID,
     MediaStore.Audio.Playlists.Members.TITLE,
     };
Uri membersUri = MediaStore.Audio.Playlists.Members.getContentUri(volume, playlistId);
Cursor tCursor = managedQuery(membersUri, columns, null, null, null);

我不知道 volume 参数需要是什么。我试过这个:MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI.toString() 用于“音量”参数。

这会返回一个有效的内容 URI，如下所示:

content://media/external/audio/playlists/2/members

但是，我的光标返回为空。我可能离题太远了——我知道我想做的很简单。

Answer 1

字符串“external”在 MediaStore.Audio.Playlists.Members.getContentUri(volume, playlistId) 中用作音量

此 Activity 打印 Android 上的歌曲、播放列表及其内容。

import android.app.Activity;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;

public class PlaylistActivity extends Activity {
    private final String [] STAR= {"*"};
    private final String TAG= "list";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

        Log.i(TAG, "All the titles");
        Uri allaudio_uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        Cursor ca= managedQuery(allaudio_uri, STAR, null,null,null);
        for(ca.moveToFirst(); !ca.isAfterLast(); ca.moveToNext()){
            if(ca.isFirst()){   // print all the fields of the first song
                for(int k= 0; k<ca.getColumnCount(); k++)
                    Log.i(TAG, "  "+ca.getColumnName(k)+"="+ca.getString(k));
            }else{              // but just the titles of the res
                Log.i(TAG, ca.getString(ca.getColumnIndex("title")));
            }
        }
        Log.i(TAG, "--------------------------");
        Log.i(TAG, "All the playlists");
        Uri playlist_uri= MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI;    
        Cursor cursor= managedQuery(playlist_uri, STAR, null,null,null);
        cursor.moveToFirst();
        for(int r= 0; r<cursor.getCount(); r++, cursor.moveToNext()){
            Log.i(TAG, "-----");
            Log.i(TAG, "Playlist " + cursor.getString(cursor.getColumnIndex("name")));
            for(int k= 0; k<cursor.getColumnCount(); k++)           
                Log.i(TAG, cursor.getColumnName(k)+"="+cursor.getString(k));

            // the members of this playlist
            int id= cursor.getInt(0);
            Uri membersUri = MediaStore.Audio.Playlists.Members.getContentUri("external", id);
            Cursor membersCursor = managedQuery(membersUri, STAR, null, null, null);
            membersCursor.moveToFirst();
            for(int s= 0; s<membersCursor.getCount(); s++, membersCursor.moveToNext())
                Log.i(TAG, "  "+membersCursor.getString(membersCursor.getColumnIndex("title")));
            membersCursor.close();
        }
        cursor.close();
    }
}