I searched and found what looked like the exact question I have (http://stackoverflow.com/questions/4369537/update-ui-from-thread). Unfortunately I'm still not able to get this working.
I have an ImageView on my layout. When a button is pressed, a ProgressDialog is created and shown. As the thread processes data, it calls the incrementProgressBy() method on a handler in the UI. Inside that handler, I update the ImageView using setImageBitmap(), and then I Invalidate it. It never updates. Next, I tried calling ImageView.postInvalidate() from the progress bar's thread. It still does not update until the progress bar completes and is removed.
Any ideas?