Efficient Album Cover loading for ListView
Your lag will be coming from this line:

 Bitmap coverBitmap = BitmapFactory.decodeFile(cursor.getString(holder.column3));


Your right about doing it asyncrhonously.
You could also scale the image.

What you'll want to do is:


spawn a new thread
use a handler for when the bitmap has decoded
set the bitmap on the imageview in the callback


You could set the image to a spinner whilst it is loading.

An example of something similar is:

http://blog.blundellapps.co.uk/imageview-with-loading-spinner/

And an example of image scaling is:

http://developer.android.com/training/displaying-bitmaps/load-bitmap.html#load-bitmap