Question

I am making an android application where there are news articles with a thumbnail. Those thumbnails are loaded from network and stored in a LruCache with the URL as the key, and the bitmap as the value.

private LruCache<String, Bitmap> tCache;

in the getView() method of the adapter, I call getThumbnail() which checks the cache (load from network when necessary) then show the thumbnail.

public void populateList(){
    ...
    new Thread(new Runnable() {
        @Override
        public void run() {
            getThumbnail(story, thumbnail);
        }
    }).start();
}

and

private Bitmap getThumbnail(Story story, ImageView imageView) {
    String url = story.getThumbnail();

    Bitmap bitmap;
    synchronized (tCache) {
        bitmap = tCache.get(url);

        if (bitmap == null) {

            bitmap = new ImageLoadingUtils(this, imageView).execute(url,
                    Boolean.TRUE).get();
            tCache.put(url, bitmap);

        }
    }
    return bitmap;

}

The ImageLoadingUtils loads from network and puts the resulting bitmap in the ImageView when done.

@Override
protected void onPostExecute(Bitmap result) {
    if (imageView != null) {
        imageView.setImageBitmap(result);
        adapter.notifyDataSetChanged();
    }
}

The problem is the thumbnails get repeated in the same ListView when I scroll down.

________
|IMAGE1|
|IMAGE2|
|IMAGE3|  SCREEN
|IMAGE4|
--------
|IMAGE1|
|IMAGE2|  OFFSCREEN
________

And the articles don’t have the correct thumbnails anymore when I scroll down then back up. It’s very messed up.

Anyone can spot the issue? Thank you a lot.

Answer 1

The problem is because the Views are reused in a listview. Here is a good example on how to cache and load thumbnails asynchronously in listview.

Lazy Load ListView Android