Question

我是android新手。我正在使用服务实现音乐播放器。以下是错误集中的代码。任何人都可以帮我解决这个错误吗？

public void getSong() {
    ContentResolver contentResolver = getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor cursor = contentResolver.query(musicUri, null, null, null, null);

    if (cursor != null && cursor.moveToFirst()) {
        do {
            long thisId = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media._ID));
            String thisTitle = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
            String thisArtist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));

            int albumId = cursor.getColumnIndex(android.provider.MediaStore.Audio.Albums.ALBUM_ART);
            String thisArt = cursor.getString(albumId);

            musicArrayList.add(new Music(thisId, thisTitle, thisArtist, thisArt));
        } while (cursor.moveToNext());
    }
}

Answer 1

确保用于获取具有相同列名的数据的表看看这个http://www.rjkfw.com/android/s3035.html

Answer 2

在提取数据之前检查null。

ListView audioListView = (ListView) findViewById(R.id.songView);

   ArrayList<string> audioList = new ArrayList<>();

   String[] proj = { MediaStore.Audio.Media._ID,MediaStore.Audio.Media.DISPLAY_NAME };// Can include more data for more details and check it.

   Cursor audioCursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, proj, null, null, null);

   if(audioCursor != null){
       if(audioCursor.moveToFirst()){
           do{
               int audioIndex = audioCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME);

               audioList.add(audioCursor.getString(audioIndex));
           }while(audioCursor.moveToNext());
       }
   }
   audioCursor.close();

   ArrayAdapter<string> adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,android.R.id.text1, audioList);
   audioListView.setAdapter(adapter);

Answer 3

错误解决，因为我正在寻找特定歌曲的专辑，所以在游标中传递空值。所以我改变了我的光标代码如下：

public void getSong() {

        ContentResolver contentResolver = getContentResolver();
        Cursor cursor = contentResolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                new String[]{MediaStore.Audio.Media._ID,
                        MediaStore.Audio.Media.TITLE,
                        MediaStore.Audio.Media.ARTIST,
                        MediaStore.Audio.Media.ALBUM},
                MediaStore.Audio.Media.IS_MUSIC + "=1",
                null,
                null);


        if (cursor != null && cursor.moveToFirst()) {
            do {
                long thisId = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media._ID));
                String thisTitle = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE));
                String thisArtist = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST));
                String thisImage = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ALBUM));

                songList.add(new Music(thisId, thisTitle, thisArtist, thisImage));
}while (cursor.moveToNext());
}

我尝试在服务类的playSong（）中调用getsongImage（URI）方法来获取Album，如下所示：

public void getSongImage(Uri uri) {
        MediaMetadataRetriever mmr = new MediaMetadataRetriever();
        mmr.setDataSource(this,uri);
        byte [] data = mmr.getEmbeddedPicture();
        if(data==null){
            activitySongDetailBinding.imgMusic.setImageResource(R.drawable.img);
        }else {
            Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            activitySongDetailBinding.imgMusic.setImageBitmap(bitmap);
        }
    }

其中uri = ContentUris.withAppendedId（ android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI，songsArrayList.get（songPosn）.getId（））

IllegalStateException：无法从CursorWindow读取第0行，col -1。在从中访问数据之前，请确保正确初始化Cursor

3 个答案: