If you're changing the layout of an existing ImageView, you should be able to simply get the current LayoutParams, change the width/height, and set it back:
android.view.ViewGroup.LayoutParams layoutParams = myImageView.getLayoutParams();
layoutParams.width = 30;
layoutParams.height = 30;
myImageView.setLayoutParams(layoutParams);
I don't know if that's your goal, but if it is, this is probably the easiest solution.