Flutter 为 DraggableScrollableSheet 设置自定义高度

Question

当我使用DraggableScrollableSheet时，我遇到了一些问题，它们是：

1. 将其拖到底部后如何设置最小高度
2. 如何设置最小高度
3. 如何设置最大高度
4. 我怎么知道像粘在appBar上一样粘在顶部，检测最大尺寸

SizedBox.expand(
  child: SlideTransition(
    position: _draggableBottomSheetTween.animate(_draggableBottomSheetController),
    child: DraggableScrollableSheet(
      builder: (BuildContext context, ScrollController scrollController) {
        return ClipRRect(
          borderRadius: BorderRadius.only(
            topLeft: Radius.circular(10.0),
            topRight: Radius.circular(10.0)
          ),
          child: Container(
            height: 500.0,
            color: pageBackgroundColor,
            child: ListView.builder(
              controller: scrollController,
              itemCount: 5,
              itemBuilder: (BuildContext context, int index) {
                return ListTile(title: Text('Item $index'));
              },
            ),
          ),
        );
      },
    ),
  ),
),

Answer 1

这是完整的解决方案。

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Duration _duration = Duration(milliseconds: 500);
  Tween<Offset> _tween = Tween(begin: Offset(0, 1), end: Offset(0, 0));
  double _height, min = 0.1, initial = 0.3, max = 0.7;
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this, duration: _duration);
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: GestureDetector(
        child: FloatingActionButton(
          child: AnimatedIcon(icon: AnimatedIcons.menu_close, progress: _controller),
          elevation: 5,
          backgroundColor: Colors.deepOrange,
          foregroundColor: Colors.white,
          onPressed: () async {
            if (_controller.isDismissed)
              _controller.forward();
            else if (_controller.isCompleted) _controller.reverse();
          },
        ),
      ),
      body: SizedBox.expand(
        child: Stack(
          children: <Widget>[
            FlutterLogo(size: 500),
            SizedBox.expand(
              child: SlideTransition(
                position: _tween.animate(_controller),
                child: DraggableScrollableSheet(
                  minChildSize: min, // 0.1 times of available height, sheet can't go below this on dragging
                  maxChildSize: max, // 0.7 times of available height, sheet can't go above this on dragging
                  initialChildSize: initial, // 0.1 times of available height, sheet start at this size when opened for first time
                  builder: (BuildContext context, ScrollController controller) {
                    if (controller.hasClients) {
                      var dimension = controller.position.viewportDimension;
                      _height ??= dimension / initial;
                      if (dimension >= _height * max * 0.9)
                        print("at top");
                      else if (dimension <= _height * min * 1.1)
                        print("at bottom");
                    }
                    return ClipRRect(
                      borderRadius: BorderRadius.only(topLeft: Radius.circular(20.0), topRight: Radius.circular(20.0)),
                      child: Container(
                        height: 500.0,
                        color: Colors.blue[800],
                        child: ListView.builder(
                          controller: controller,
                          itemCount: 5,
                          itemBuilder: (BuildContext context, int index) {
                            return ListTile(title: Text('Item $index'));
                          },
                        ),
                      ),
                    );
                  },
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}