Question

I have a ListView which contains an ImageView and a TextView. I’m subclassing ArrayAdapter so that I can load an image from the internet, via a subclassed AsyncTask. All good so far.

The problem is that if I try to use convertView, I have a problem where the image is recycled briefly into the wrong row. (This is a company’s logo, so this is… not good.)

If I don’t use convertView, however, the image is lost when the user scrolls. So if they scroll down and back up, the image is re-loaded from the internet (which is obviously bad for data use, battery life etc.)

Is there a simple way to fix this so that it doesn’t load from the internet each time, or move the images around?

Here’s what I’m using so far:

public class SupplierAdapter extends ArrayAdapter<Supplier>{
    int resource;
    String response;
    Context context;

    public SupplierAdapter(Context context, int resource, List<Supplier> suppliers) {
        super(context, resource, suppliers);
        this.resource = resource;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent){
    LinearLayout view;
        Supplier s = getItem(position);

        if(convertView == null){
            view = new LinearLayout(getContext());
            String inflater = Context.LAYOUT_INFLATER_SERVICE;
            LayoutInflater vi;
            vi = (LayoutInflater) getContext().getSystemService(inflater);
            vi.inflate(resource, view, true);
        } else {
            view = (LinearLayout) convertView;
        }

        ImageView iv = (ImageView) view.findViewById(R.id.thumbnail);
        // s.getThumbnail returns a URL
        new DownloadImageTask(iv).execute(s.getThumbnail()); 

        TextView titleText =(TextView) view.findViewById(R.id.titleText);
        titleText.setText(s.getTitle());
        titleText.setTag(s.getId());

        return view;
    }
}

All help very much appreciated 🙂

Answer 1

John, try using raptureinvenice.com‘s WebImageView. I recently refactored my code to use this easy and lightweight library and so far, so good. It easily provides a two level cache, updates multiple targets simultaneously, and was incredibly easy to set up. It looks like it seems to drop about 1/20 requests to display an image. Other than this lurking bug that could be the library’s fault, it is excellent.