如何知道DraggableScrollableSheet是折叠的还是展开的

ScrollController _scrollController = ScrollController();
bool _isExpanded = true;

@override
void initState() {
  super.initState();
  _scrollController.addListener(_handleScroll);
}

void _handleScroll() {
  if (_scrollController.offset <= _scrollController.position.minScrollExtent) {
    setState(() {
      _isExpanded = true;
    });
  } else if (_scrollController.offset >= _scrollController.position.maxScrollExtent) {
    setState(() {
      _isExpanded = false;
    });
  }
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text('DraggableScrollableSheet Demo'),
    ),
    body: Stack(
      children: [
        ListView.builder(
          controller: _scrollController,
          itemCount: 100,
          itemBuilder: (context, index) {
            return ListTile(
              title: Text('Item $index'),
            );
          },
        ),
        DraggableScrollableSheet(
          initialChildSize: 0.5,
          minChildSize: 0.2,
          maxChildSize: 0.8,
          builder: (context, scrollController) {
            return Container(
              color: Colors.grey,
              child: ListView.builder(
                controller: scrollController,
                itemCount: 10,
                itemBuilder: (context, index) {
                  return ListTile(
                    title: Text('Sheet Item $index'),
                  );
                },
              ),
            );
          },
        ),
      ],
    ),
  );
}