code: @Override
      public void onScroll(
              AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
          SimpleMonthView child = (SimpleMonthView) view.getChildAt(0);
          if (child == null) {
              return;
          }
  
          // Figure out where we are
          long currScroll = view.getFirstVisiblePosition() * child.getHeight() - child.getBottom();
          mPreviousScrollPosition = currScroll;
          mPreviousScrollState = mCurrentScrollState;
      }
docs: Updates the title and selected month if the view has moved to a new
  month.