Just support static XML not suport dynamic addView

[AlexMofer]

Use ViewGroup's addView, will Crash on onLayout.
Use ViewGroup's addView(View, LayoutParams) with PhysicsFrameLayout.LayoutParams(context, null), will also Crash on onLayout.
Missing two override:

        @Override
        protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
            return p instanceof LayoutParams;
        }

        @Override
        protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
            return new LayoutParams(lp);// Add a constructor.
        }

       // Optional
       @Override
        protected FrameLayout.LayoutParams generateDefaultLayoutParams() {
            return new LayoutParams(getContext(), null);
        }

PhysicsFrameLayout.LayoutParams does not actually support null AttributeSet.