flutter - 如何使用 Navigator.popUntil Flutter

Question

我正在做一个 Flutter 应用程序，我想从第 4 页返回到第 1 页。
我有一个非常奇怪的错误:

Bad state : Future already completed

我创建了一个简单的项目来重现这个错误:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      onGenerateRoute: routes,
    );
  }
}

Route routes(RouteSettings settings) {
  if (settings.name == '/page1') {
    return MaterialPageRoute(
      builder: (context) {
        return Page1();
      },
    );
  } else if (settings.name == '/page2') {
    return MaterialPageRoute(
      builder: (context) {
        return Page2();
      },
    );
  } else if (settings.name == '/page3') {
    return MaterialPageRoute(
      builder: (context) {
        return Page3();
      },
    );
  } else if (settings.name == '/page4') {
    return MaterialPageRoute(
      builder: (context) {
        return Page4();
      },
    );
  } else {
    return MaterialPageRoute(
      builder: (context) {
        return Page1();
      },
    );
  }
}

class Page1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Page 1'),
            RaisedButton(
              child: Text('Go Page 2'),
              onPressed: () {
                Navigator.of(context).pushNamed('/page2');
              },
            )
          ],
        ),
      ),
    );
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Page 2'),
            RaisedButton(
              child: Text('Go Page 3'),
              onPressed: () {
                Navigator.of(context).pushNamed('/page3');
              },
            )
          ],
        ),
      ),
    );
  }
}

class Page3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Page 3'),
            RaisedButton(
              child: Text('Go Page 4'),
              onPressed: () {
                Navigator.of(context).pushNamed('/page4');
              },
            )
          ],
        ),
      ),
    );
  }
}

class Page4 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Page 4'),
            RaisedButton(
              child: Text('Go Back Page 1'),
              onPressed: () {
                Navigator.of(context).popUntil(ModalRoute.withName('/page1'));
              },
            )
          ],
        ),
      ),
    );
  }
}

我该如何解决？

Answer 1

这是重复的问题。引用 this和 this .

基本上发生的事情是 - 当您启动应用程序时，page1 打开，因为它进入最后一个 else 并且没有为其分配名称，因此当您执行 popuntil 该页面名称时，它根本找不到它。