调用setState后如何防止Flutter应用滚动到顶部？ [英] How to prevent Flutter app from scrolling to top after calling setState?

问题描述

我在 SingleChildScrollView 中有一个 ExpansionPanelList 。每当我打开面板并因此调用 setState 时， SingleChildScrollView 都会滚动回到顶部。如何防止这种情况发生？

I have an ExpansionPanelList inside a SingleChildScrollView. Whenever I (un)fold a panel and therefore call setState, the SingleChildScrollView scrolls back to the top. How can I prevent this?

@override
Widget build(BuildContext context) {
  final _scaffoldKey = new GlobalKey<ScaffoldState>();
  return new Scaffold(
    key: _scaffoldKey,
    appBar: new AppBar(
      title: new Text(widget.title),
    ),
    body: new SingleChildScrollView(
      child: new ExpansionPanelList(
        children: <ExpansionPanel>[
          // panels
        ],
        expansionCallback: (int index, bool isExpanded) {
          setState(() {
            // toggle expanded
          });
        },
      ), // ExpansionPanelList
    ), // SingleChildScrollView
  ); // Scaffold
}

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此答案建议使用带有 keepScrollOffset的自定义 ScrollController 设置为 true ，但这是默认值，因此将其显式设置为 true 不会更改任何内容。

---

This answer suggests using a custom ScrollController with keepScrollOffset set to true, however this is the default value and setting it explicitly to true therefore does not change anything.

推荐答案

这是因为您使用的是新的 Key 每次重建窗口小部件（setState）时。

That's because you are using a new Key every time you rebuild the widget (setState).

要解决您的问题，只需将下面的代码移至 build 方法之外

To fix your issue just move the code below outside the build method

 final _scaffoldKey = new GlobalKey<ScaffoldState>(); 

就像这样：

 final _scaffoldKey = new GlobalKey<ScaffoldState>();

    @override
    Widget build(BuildContext context) {
      return new Scaffold(
        key: _scaffoldKey,
        appBar: new AppBar(
          title: new Text(widget.title),
        ),

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