Question

For some reason my custom adapter is only allowing me to have 1 image visible in the list view at any time, I am not sure why this is happening. There should be a image within each list item but only the last list item has its image set, so I assume I am re-using a value somewhere that I should not be. The rest of the list items are being set properly.

public class CustomAdapter extends ArrayAdapter<Item> {

    private ArrayList<Item> itemList;
    private ViewHolder holder; 
    private Context context;

    public CustomAdapter(Context context, int textViewResourceId, ArrayList<Item> list) {
        super(context, textViewResourceId, list);
        this.itemList = new ArrayList<Item>();
        this.itemList.addAll(list);
        this.context = context;
    }

    private class ViewHolder {
        ImageView img;
        TextView name;
        CheckBox access;
    }

    @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.list_grid, null);

            holder = new ViewHolder();
            holder.name = (TextView) convertView.findViewById(R.id.name);
            holder.access = (CheckBox) convertView.findViewById(R.id.checkBox1);
            holder.img = (ImageView) convertView.findViewById(R.id.imageView1);

            convertView.setTag(holder);
        } 

        else { holder = (ViewHolder) convertView.getTag(); }

        Item it = itemList.get(position);

        new UrlLookup().execute(it.getUrl());
        holder.name.setText(it.getName());
        holder.access.setChecked(it.isSelected());

        return convertView;
    }

    //Create an image from the url passed in from the server and display it on the image view   
    private class UrlLookup extends AsyncTask<String, Integer, String>{
        Bitmap bmp;

        @Override
        protected String doInBackground(String... params){  
            try {
                URL u = new URL(params[0]);
                bmp = BitmapFactory.decodeStream(u.openConnection().getInputStream());
            } catch (Exception e) { e.printStackTrace(); }

            return "Done!";
        }

        @Override
        protected void onPostExecute(String result){
            super.onPostExecute(result);    
            holder.img.setImageBitmap(bmp);
        }
    }
}

Answer 1

You’re forgetting the fact that your holder changes every time a view is visible. So it’s normal only the last item has an image.

AsyncTask will take considerably longer to finish than your getView method.

You should pass your ImageView to your AsyncTask:

new UrlLookup().execute(it.getUrl(), holder.img);

To call the AsyncTask

private class UrlLookup extends AsyncTask<Object, Integer, String>{
    Bitmap bmp;
    ImageView view;

    @Override
    protected String doInBackground(Object... params){ 
        view = (ImageView) params[1]; 
        try {
            URL u = new URL((String)params[0]);
            bmp = BitmapFactory.decodeStream(u.openConnection().getInputStream());
        } catch (Exception e) { e.printStackTrace(); }

        return "Done!";
    }

    @Override
    protected void onPostExecute(String result){
        super.onPostExecute(result);    
        view.setImageBitmap(bmp);
    }
}

Now you will have a reference of the ImageView of every row in every AsyncTask.

I would like to point out to you that Koush has a splendid project for doing just what you want:
UrlImageViewHelper