code: @Override
      protected void onSizeChanged(int w, int h, int oldw, int oldh) {
          super.onSizeChanged(w, h, oldw, oldh);
  
          mGraph.setPivot(mGraphBounds.centerX(), mGraphBounds.centerY());
  
          onDataChanged();
      }
docs: This is called during layout when the size of this view has changed. If
  you were just added to the view hierarchy, you're called with the old
  values of 0.
  
  @param w    Current width of this view.
  @param h    Current height of this view.
  @param oldw Old width of this view.
  @param oldh Old height of this view.