code: @Override
      protected void onDraw(Canvas canvas) {
          super.onDraw(canvas);
  
          // If the API level is less than 11, we can't rely on the view animation system to
          // do the scrolling animation. Need to tick it here and call postInvalidate() until the scrolling is done.
          if (Build.VERSION.SDK_INT < 11) {
              tickScrollAnimation();
              if (!mScroller.isFinished()) {
                  mGraph.postInvalidate();
              }
          }
      }
docs: Implement this to do your drawing.
  
  @param canvas the canvas on which the background will be drawn