使用onGenerateRoute在屏幕之间进行条件退出转换

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      onGenerateRoute: (settings) {
        if (settings.name == '/') {
          // 根据条件返回不同的路由
          if (isLoggedIn()) {
            return MaterialPageRoute(builder: (_) => HomeScreen());
          } else {
            return MaterialPageRoute(builder: (_) => LoginScreen());
          }
        }
        // 如果无法找到指定路由，则返回错误页面
        return MaterialPageRoute(builder: (_) => ErrorScreen());
      },
    );
  }

  bool isLoggedIn() {
    // 根据具体的登录逻辑判断用户是否已登录
    // 返回true表示已登录，返回false表示未登录
    return true;
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Center(
        child: Text('Welcome to the Home Screen!'),
      ),
    );
  }
}

class LoginScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Login'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Login'),
          onPressed: () {
            // 执行登录操作
            // 登录成功后，使用Navigator.pushReplacementNamed方法跳转到主屏幕
            Navigator.pushReplacementNamed(context, '/');
          },
        ),
      ),
    );
  }
}

class ErrorScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Error'),
      ),
      body: Center(
        child: Text('Error: Page not found!'),
      ),
    );
  }
}