提供者：查找已停用小部件的祖先是不安全的

Posted 2023-02-23

【中文标题】提供者：查找已停用小部件的祖先是不安全的

【英文标题】：Provider : Looking up a deactivated widget's ancestor is unsafe

【发布时间】：2020-12-26 19:28:00

【问题描述】：

尝试从提供者那里获取值，它工作正常，但我收到以下错误。我在这里做错了什么？

  @override
  Widget build(BuildContext context) 
    String route = Provider.of<User>(context) == null ? Router.LOGIN : Router.HOME;
    Future.delayed(const Duration(seconds: 2), () => Navigator.pushReplacementNamed(context, route));

    return Scaffold(........

错误

E/flutter (23058): [ERROR:flutter/shell/common/shell.cc(209)] Dart Error: Unhandled exception:
E/flutter (23058): Looking up a deactivated widget's ancestor is unsafe.
E/flutter (23058): At this point the state of the widget's element tree is no longer stable.
E/flutter (23058): To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.

【参考方案1】：

问题在于无法等待导航器调用。如果您需要在构建时导航到正确的页面，则创建一个没有返回类型的异步方法，然后在 initState 中调用该方法。

_checkUserExistsAndNavigate() async 
  String route = Provider.of<User>(context) == null ? Router.login : Router.home;
await Future.delayed(seconds: 2), () => Navigator.pushReplacementNamed(context, route);


@initState(() 
_checkUserExistsAndNavigate();
super.initState();