Images are repeating in ListView

Aha! I think I may know the issue. Right now, your getView method sets your ImageView like this:

1. Gets movie object at position
2. Pulls out the movie's thumbnail url
3. Using that url, it tries to find the image in the cache
4. If it finds the image, it sets it
5. If it can't find the image, it starts an async network request to go get it, and sets it after it gets downloaded.

Your issus arises since ListView reuses its rows' Views. When the first View scrolls off the screen, rather than inflate a new one, ListView passes the now offscreen row's View in as convertView for you to reuse (this is for efficiency).

When your getView gets a convertView that is getting reused, its ImageView has already been set from the row that had it before, so you see the old image from the offscreen row's View. With your current getView process, you check for the new row's image, and it doesn't find it in the cache, it starts a request to download it. While it is downloading, you see the old image until you get the new image.

To fix this, you need to make sure you set every field in the row's View immediately, to make sure you don't have any Views showing stale data. I would suggest you set the ImageView to the default drawable resource (you have set in your R.layout.movie_data_row) while you wait for the network download to get the image.

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = vi.inflate(R.layout.movie_data_row, null);
    }

    ParkCinema movie = movieDataItems.get(position);
    ImageView imageView = (ImageView) convertView.findViewById(R.id.movie_thumb_icon);
    if (movie != null) {
        String url = movie.poster();

        if (url != null) {
            Bitmap bitmap = fetchBitmapFromCache(url);
            if (bitmap == null) {
                // Set the movie thumbnail to the default icon while we load
                // the real image
                imageView.setImageResource(R.drawable.movie_thumb_icon);
                new BitmapDownloaderTask(imageView).execute(url);
            }
            else {
                // Set the image to the bitmap we get from the cache
                imageView.setImageBitmap(bitmap);
            }
        }
        else {
            // Set the movie thumbnail to the default icon, since it doesn't
            // have a thumbnail URL
            imageView.setImageResource(R.drawable.movie_thumb_icon);
        }
    }
    else {
        // Set the movie thumbnail to the default icon, since there's no
        // movie data for this row
        imageView.setImageResource(R.drawable.movie_thumb_icon);
    }

-Edit-

Updated to be even more robust, using your drawable. You also have an issue with your BitmapDownloaderTask, it does not handle errors/null. Try adding this as well.

@Override
protected void onPostExecute(Bitmap bitmap) { 
    addBitmapToCache(url, bitmap);
    if (bitmap == null) {
        // Set the movie thumbnail to the default icon, since an error occurred while downloading
        imageViewReference.get().setImageResource(R.drawable.movie_thumb_icon);
    }
    else {
        imageViewReference.get().setImageBitmap(bitmap);
    }            
}