如何在游标适配器中使用albumArt加载AsyncTask

Question

在检索albumArt并使用游标适配器中的AsyncTask将该艺术设置为ImageView时，我遇到了问题。当我打开我的应用程序时，它看起来如下：

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然后我向下滚动列表，一切都很好(如果我滚动列表不是很快的话)：

​

然后我滚动列表返回到非常乞讨(不是很快)，它看起来也很好：

​

我想，我可能做错了什么，所以我有疑问：

是否有可能以某种方式解决这个问题，我已经尝试过许多不同的方法来实现AsyncTask并使其正常工作，但最终它看起来总是一样的。

下面是游标适配器的代码：

public class AllSongsCursorAdapter extends CursorAdapter {

public AllSongsCursorAdapter(Context context, Cursor cursor) {
    super(context, cursor, 0);
}

public boolean isCheckBoxVisible;
private AddToFavouritesArray favouritesArray = AddToFavouritesArray.getInstance();

private static class ViewHolder {
    CheckBox checkBox;
    TextView title;
    TextView artist;
    ImageView albumArt;

    private ViewHolder(View view) {

        checkBox = (CheckBox) view.findViewById(R.id.favouritesCheckBox);
        title = (TextView) view.findViewById(R.id.title);
        artist = (TextView) view.findViewById(R.id.artist);
        albumArt = (ImageView) view.findViewById(R.id.albumArt);
    }
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup viewGroup) {
    View view = LayoutInflater.from(context).inflate(R.layout.song_item, viewGroup, false);
    ViewHolder viewHolder = new ViewHolder(view);
    view.setTag(viewHolder);
    return view;
}

@Override
public void bindView(View view, Context context, final Cursor cursor) {

    final ViewHolder viewHolder = (ViewHolder) view.getTag();
    if (isCheckBoxVisible) {
        viewHolder.checkBox.setVisibility(View.VISIBLE);
    } else {
        viewHolder.checkBox.setVisibility(View.GONE);
    }

    final int position = cursor.getPosition();
    viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {

            if (b) {
                favouritesArray.integerArray.add(position);

            } else {
                favouritesArray.integerArray.remove(Integer.valueOf(position));
            }
        }
    });

    int songTitle = cursor.getColumnIndex(MediaStore.Audio.Media.TITLE);
    int songArtist = cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST);

    String currentTitle = cursor.getString(songTitle);
    String currentArtist = cursor.getString(songArtist);

    viewHolder.title.setText(currentTitle);
    viewHolder.artist.setText(currentArtist);

    //__________________________ALBUM_ART_______________________________________________________

    viewHolder.albumArt.setTag(cursor.getPosition());

    new AsyncTask<ViewHolder, Void, Bitmap>(){

        private ViewHolder viewHolder;

        @Override
        protected Bitmap doInBackground(ViewHolder... viewHolders) {
            viewHolder = viewHolders[0];
            int id = cursor.getColumnIndex(MediaStore.Audio.Media._ID);
            long songId = cursor.getLong(id);

            Bitmap albumArt = getAlbumId(context, songId);
            return albumArt;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            super.onPostExecute(bitmap);
            if(bitmap != null) {
                viewHolder.albumArt.setImageBitmap(bitmap);
            }else{
                viewHolder.albumArt.setImageResource(R.drawable.placeholder);
            }
        }
    }.execute(viewHolder);
}

private Bitmap getAlbumId(Context context, long id) {

    Bitmap albumArt = null;
    String selection = MediaStore.Audio.Media._ID + " = " + id + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{
                    MediaStore.Audio.Media._ID, MediaStore.Audio.Media.ALBUM_ID},
            selection, null, null);
    if (cursor.moveToFirst()) {
        long albumId = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));

        albumArt = getAlbumArt(context, albumId);
    }
    cursor.close();
    return albumArt;

}

private Bitmap getAlbumArt(Context context, long albumId) {

    Bitmap albumArt = null;
    String selection = MediaStore.Audio.Albums._ID + " = " + albumId + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI, null, selection, null, null);

    if (cursor.moveToFirst()) {

        int art = cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM_ART);

        String currentArt = cursor.getString(art);
        albumArt = BitmapFactory.decodeFile(currentArt);
    }
    cursor.close();
    return albumArt;
}

}

是的，当然，没有AsyncTask，除了滚动之外，一切都很好。提前谢谢你！

编辑

到头来，这就是它的工作原理。非常感谢你@ Orest Savchak，我对你的回答投赞成票和接受。非常感谢。//__________________________ALBUM_ART_______________________________________________________

    int id = cursor.getColumnIndex(MediaStore.Audio.Media._ID);
    long songId = cursor.getLong(id);
    String string = getAlbumArtPath(context, songId);
    if(string!=null) {
        Picasso.with(context)
                .load(new File(string))
                .into(viewHolder.albumArt);
    }else{
        viewHolder.albumArt.setImageResource(R.drawable.placeholder);
    }
}
private String getAlbumArtPath(Context context, long id) {

    String selection = MediaStore.Audio.Media._ID + " = " + id + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{
                    MediaStore.Audio.Media._ID, MediaStore.Audio.Media.ALBUM_ID},
            selection, null, null);
    if (cursor.moveToFirst()) {
        long albumId = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));

        return getAlbumArt(context, albumId);
    }
    cursor.close();
    return null;

}

private String getAlbumArt(Context context, long albumId) {

    String selection = MediaStore.Audio.Albums._ID + " = " + albumId + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI, null, selection, null, null);

    if (cursor.moveToFirst()) {

        int art = cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM_ART);

        return cursor.getString(art);
    }
    cursor.close();
    return null;
}

Answer 1

你应该自己管理你的任务。您的视图是可回收的，因此，对于不同的行只有一个视图，这会导致问题。大多数项目使用一些库，这些库为您自动完成--要容易得多，例如毕加索。

Picasso.with(context).load(new File(getAlbumArtPath(context, songId))).into(viewHolder.albumArt);

private String getAlbumArtPath(Context context, long id) {

    String selection = MediaStore.Audio.Media._ID + " = " + id + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{
                    MediaStore.Audio.Media._ID, MediaStore.Audio.Media.ALBUM_ID},
            selection, null, null);
    if (cursor.moveToFirst()) {
        long albumId = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));

        return getAlbumArt(context, albumId);
    }
    cursor.close();
    return null;

}

private String getAlbumArt(Context context, long albumId) {

    String selection = MediaStore.Audio.Albums._ID + " = " + albumId + "";
    Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI, null, selection, null, null);

    if (cursor.moveToFirst()) {

        int art = cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM_ART);

        return cursor.getString(art);
    }
    cursor.close();
    return null;
}