Android ViewGroup: what should I do in the onLayout() override?

In onLayout you need to call layout method on each child of this ViewGroup and provide desired position (relatively to parent) for them. You can check source code of FrameLayout (one of the simpliest subclasses of ViewGroup) to find out how it works.

Although, if you don’t need any “special” layouting, you have other options:

• Extend some another subclass of ViewGroup instead (FrameLayout for example)
• Use LayoutInflater if you just need your control to look exactly as in XML (which, I think, is exactly your case)