code: @Override
      protected void onSizeChanged(int w, int h, int oldw, int oldh) {
          super.onSizeChanged(w, h, oldw, oldh);
          // Check if the current graph is a VerticalBarChart and set the
          // availableScreenSize to the chartHeight
          mAvailableScreenSize = this instanceof VerticalBarChart ? mGraphHeight : mGraphWidth;
  
          if(getData().size() > 0) {
              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.