Flutter ListView、SliverList 等中的当前滚动偏移

Question

如何在 Flutter ListView, SliverList等中获取当前滚动偏移量？

Answer 1

• If you're inside the scroll view use Scrollable.of(context).position.pixels .
• If you're outside, you probably want to hand a ScrollController in as the controller argument of the scroll view, then you can read controller.offset .
• Alternatively, use scroll notifications with NotificationListener .

This was asked on Flutter Gitter, and answered: https://gitter.im/flutter/flutter?at=591243f18a05641b1167be0e

Answer 2

For someone else, looking for code implementation, you can use ScrollController like this:

ScrollController _scrollController;

@override
void initState() {
  super.initState();
  _scrollController = ScrollController()
    ..addListener(() {
      print("offset = ${_scrollController.offset}");
  });
}

@override
Widget build(BuildContext context) {
  return ListView(
    controller: _scrollController, 
    children: <Widget>[],
  );
}

@override
void dispose() {
  _scrollController.dispose(); // it is a good practice to dispose the controller
  super.dispose();
}

Answer 3

Another approach is with NotificationListener

NotificationListener(
  child: ListView(
    controller: _scrollController,
    children: ...
  ),
  onNotification: (notification) {
    if (notification is ScrollEndNotification) {
      print(_scrollController.position.pixels);
    }
    return false;
  },
)