Improve ListView efficiency when loading images from SD into the ListView

Question

I am using a custom adapter for my ListView as per the efficient adapter sample by Romain Guy.

In the getView() method of my adapter I am assigning an ImageView a jpg image stored on SD using the following code :

File f=new File(MovieThumbs.get(position));

if(f.length() > 0) {
    holder.thumb.setImageBitmap(BitmapFactory.decodeFile(MovieThumbs.get(position)));
}

When flicking through a list of some 200 items using this method the app suffers from bad stuttering as it tries dealing with the images.

Is there a more efficient solution for this?

Answer 1

Rather than loading the images from within the list adapter on demand how about kicking off a thread from the onCreate of your activity to load images? As each image loads you can fire a callback to the activity to display the image in the list. The callback method would be something along the lines of:

void onImageDownloadComplete(int pos, BitMap bm) {
    ListView lv = getListView();
    View listItem = lv.getChildAt(pos);
    ImageView img = (ImageView)listItem.getChildAt(indexOfIcon);
    img.setImageBitmap(bm);
}

Answer 2

Images need to be processed in background thread. Recycled views need to be taken into account. I try to address all these issues in my sample code, it works fine now, you may take a look http://stackoverflow.com/questions/541966/android-how-do-i-do-a-lazy-load-of-images-in-listview/3068012#3068012