childBuild method

Implementation

@override
Widget childBuild(BuildContext context) {
  return Flex(
    //次轴方向的长度，由内容决定，所以次轴的crossAxisAlignment不一定会生效
    direction: widget.direction!,
    children: reverse(),
    mainAxisAlignment: widget.mainAxisAlignment!,
    crossAxisAlignment: widget.crossAxisAlignment!,
  );
}