Android: How to optimize ListView with ImageView + 3 TextViews?

Question

I've been looking everywhere to see if there is a standard way of achieving this but I find a different solution everytime. Basically, I am trying to build a Custom ListView with an image and two-three lines of text besides it. In order to optimize it, I understand that the following have to be used:

1. convertView: Basically if the view was already inflated, use it
2. Lazy-Loading: Do not load the content of the rows until they are called for
3. Background Downloading & Caching: Download images in their own threads and then update the row (and possible cache them?)

I could manage 1 and 2 but the third one is really confusing me. Is there a best practice for this?

Thanks

Answer 1

It may be a bit early to describe something as "best practice". AsyncTask or a thread monitoring a LinkedBlockingQueue are fine ways to offload something like image fetching.

You may be interested in my ThumbnailAdapter, which handles the background downloading and caching for you.

Answer 2

Thanks to Mark for his help. This is one way of doing what he suggested (just in case some else is curious):

private class DownloadImageTask extends AsyncTask<Object, Integer, Bitmap> {

      private ImageView iv;

      protected Bitmap doInBackground(Object... params) {
       try {
        iv = (ImageView) params[0];
                 URL aURL = new URL("http://URLTOIMAGE/img" + params[1] + ".png" ); 
                 URLConnection conn = aURL.openConnection(); 
                 conn.connect(); 
                 InputStream is = conn.getInputStream(); 
                 BufferedInputStream bis = new BufferedInputStream(is); 
                 Bitmap bm = BitmapFactory.decodeStream(bis); 
                 bis.close(); 
                 is.close();
                 return bm;
            } catch (IOException e) { 
                 return null;
            } 
      }

      protected void onPostExecute(Bitmap result) {
       iv.setImageBitmap((Bitmap) result);
      }
     }

And it would be used as follows:

new DownloadImageTask().execute(new Object[] {ImageViewHandle, position});

Note that this is not a working code. This was taken from a larger code base so you will have to make appropriate changes to make this work.

Answer 3

Hey Guys I Had a look at the github code of commonsware ThumbnailAdapter but I did not find SimpleWebImageCache I think this is an Hashmap but It was no where to be found can you please help me out with this...

Answer 4

hI iM a newbie and interested to try this thumbnailadapter. Is it possible to post a snippet on how to use this in an activity? or in a custom listview adapter? thanks.