flutter GestureDetector ListView

Question

当我在GestureDetector中有一个ListView，并且我覆盖了onVerticalDragUpdate方法时，ListView不能滚动。

如何才能重写onVerticalDragUpdate方法以使ListView保持可滚动？

new GestureDetector(
              onVerticalDragUpdate: (details) => print("a"),
              child: new ListView(
                children: <Widget>[
                  new Text("a"),
                  new Text("a"),
                  new Text("a"),
                ],
              ),
            )

Answer 1

如果要检查DragUpdateDetails，可以将ListView包装在NotificationListener中。

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NotificationListener(
        onNotification: (notification) {
          if (notification is ScrollUpdateNotification) {
            print('${notification.dragDetails}');
          }
        },
        child: ListView.builder(
          itemCount: 20,
          itemBuilder: (context, index) {
            return ListTile(
              title: Text('Index = $index'),
            );
          },
        ),
      ),
    );
  }