flu valuelistenable

[sulkhibrahim]

use this to listen scroll event

ValueListenableBuilder<Iterable<ItemPosition>>(
    valueListenable: itemPositionsListener.itemPositions,
    builder: (_, b, c) {
      if (b.isNotEmpty) {
        var min = b
            .where((ItemPosition position) => position.itemTrailingEdge > 0)
            .reduce((ItemPosition min, ItemPosition position) =>
                position.itemTrailingEdge < min.itemTrailingEdge ? position : min)
            .index;
        print("min = $min");
      }
      return const SizedBox();
    })