A simple Android Layout that enables drag and zoom for child Views. You can check out the explanation on StackOverflow.
The RegionView is a subclass of a RelativeLayout, which acts as its own OnTouchListener. Simply add a View to the RegionView and it will become immediately draggable and scalable. You may limit child Views to only be dragged and scaled within the confines of RegionView by calling RegionView.setWrapContent(true).
Minimum API Level 11 (Honeycomb). (Uses View.setScaleX() and View.setScaleY(), and the likes).