可颤动拖动按下按钮时不显示可滚动工作表 [英] Flutter DraggableScrollableSheet not showing up on press of a button

问题描述

我想在我应用程序上使用DraggableScrollableSheet小部件，当我将类似的小部件与以下代码一起使用时，可以毫无问题地显示：

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('DraggableScrollableSheet'),
      ),
      body: SizedBox.expand(
        child: DraggableScrollableSheet(
          builder: (BuildContext context, ScrollController scrollController) {
            return Container(
              color: Colors.blue[100],
              child: ListView.builder(
                controller: scrollController,
                itemCount: 25,
                itemBuilder: (BuildContext context, int index) {
                  return ListTile(title: Text('Item $index'));
                },
              ),
            );
          },
        ),
      ),
    );
  }
}

但是当我想通过按例如floatingActionButton来显示时，不会显示

floatingActionButton: GestureDetector(
  child: FloatingActionButton(
    child: Icon(
      Icons.add,
      size: 35.0,
    ),
    elevation: 5,
    backgroundColor: Colors.deepOrange,
    foregroundColor: Colors.white,
    onPressed: (){
      SizedBox.expand(child: DraggableScrollableSheet(
        builder: (BuildContext context, ScrollController scrollController) {
          return Container(
            color: Colors.blue[100],
            child: ListView.builder(
              controller: scrollController,
              itemCount: 25,
              itemBuilder: (BuildContext context, int index) {
                return ListTile(title: Text('Item $index'));
              },
            ),
          );
        },
      ));
    },
  ),
),

推荐答案

如果您希望使用Animation执行此操作，以下是解决方案。

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));

  @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(
                  builder: (BuildContext context, ScrollController scrollController) {
                    return Container(
                      color: Colors.blue[800],
                      child: ListView.builder(
                        controller: scrollController,
                        itemCount: 25,
                        itemBuilder: (BuildContext context, int index) {
                          return ListTile(title: Text('Item $index'));
                        },
                      ),
                    );
                  },
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

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