The issue is that adjustViewBounds will not increase the size of the ImageView beyond the natural dimensions of the drawable. It will only shrink the view to maintain aspect ratio; if you provide a 500×500 image instead of a 50×50 image, this should work.
If you’re interested in the spot where this behavior is implemented, see ImageView.java’s onMeasure implementation.
One workaround is to implement a custom ImageView that changes this behavior in onMeasure.