如何在更新父有状态小部件时更新子有状态小部件

class ParentWidget extends StatefulWidget {
  @override
  _ParentWidgetState createState() => _ParentWidgetState();
}

class _ParentWidgetState extends State<ParentWidget> {
  int count = 0;

  void incrementCount() {
    setState(() {
      count++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        children: [
          Text('父部件计数：$count'),
          ChildWidget(count: count),
        ],
      ),
    );
  }
}

class ChildWidget extends StatefulWidget {
  final int count;

  ChildWidget({required this.count});

  @override
  _ChildWidgetState createState() => _ChildWidgetState();
}

class _ChildWidgetState extends State<ChildWidget> {
  int childCount = 0;

  @override
  void didUpdateWidget(covariant ChildWidget oldWidget) {
    if (widget.count != oldWidget.count) {
      setState(() {
        childCount = widget.count;
      });
    }
    super.didUpdateWidget(oldWidget);
  }

  @override
  Widget build(BuildContext context) {
    return Text('子部件计数：$childCount');
  }
}

@override
Widget build(BuildContext context) {
  return Container(
    child: Column(
      children: [
        Text('父部件计数：$count'),
        ChildWidget(count: count),
      ],
    ),
  );
}