initState method

Implementation

@override
void initState() {
  super.initState();
  // try to use user controllers or create them
  itemScrollController =
      widget.itemScrollController ?? ItemScrollController();
  itemPositionsListener =
      widget.itemPositionsListener ?? ItemPositionsListener.create();

  itemPositionsListener.itemPositions.addListener(_itemPositionListener);

  _selectedTabIndex.addListener(onSelectedTabChange);
}