尝试根据我的应用程序中的用户状态（是否登录）进行重定向，但由于我不确定如何在方法内部获取BuildContext，因此无法按我的意愿进行操作。

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:t2/helpers/currentuser.dart';

import 'screens/dashboard.dart';
import 'screens/login.dart';

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

CurrentUser user = new CurrentUser();

Future checkActiveUser() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();

  user.usr = prefs.get('usr');
  user.pwd = prefs.get('pwd');
  if (user.usr.length == 0 && user.usr.length == 0) {
    user.isLoggedIn = false;
    Navigator.of(x).pushNamedAndRemoveUntil('/dashboard', (Route<dynamic> route) => false);
  } else {
    // Send to login screen
    user.isLoggedIn = false;
    Navigator
        .of(x)
        .pushNamedAndRemoveUntil('/login', (Route<dynamic> route) => false);
  }

  return user.isLoggedIn;

  /*
// How to read/write to local storage
int counter = (prefs.getInt('counter') ?? 0) + 1;
print('Pressed $counter times.');
prefs.setInt('counter', counter);
*/
}

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        title: 'Flutter Demo',
        theme: new ThemeData(
          // This is the theme of your application.
          //
          // Try running your application with "flutter run". You'll see the
          // application has a blue toolbar. Then, without quitting the app, try
          // changing the primarySwatch below to Colors.green and then invoke
          // "hot reload" (press "r" in the console where you ran "flutter run",
          // or press Run > Flutter Hot Reload in IntelliJ). Notice that the
          // counter didn't reset back to zero; the application is not restarted.
          primarySwatch: Colors.blue,
        ),
        home: new MyHomePage(),
        routes: <String, WidgetBuilder>{
          '/dashboard': (BuildContext context) => new Dashboard(),
          '/login': (BuildContext context) => new Login()
        });
  }
}

class MyHomePage extends StatelessWidget {

   var isLoggedIn = checkActiveUser();

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('Demo Building'),
        ),
        body: new Container(
            child: new Center(
          child: new Column(
            children: <Widget>[new Text('DASHBOARD')],
          ),
        )));
  }
}

如果您对其他方法有任何建议，我非常高兴！我基本上想在应用程序负载上运行此检查并相应地重定向。

问候，鲍勃

更新的代码：尝试了Hadrien的建议，并且走近了一步。它现在运行，并且我可以访问联系人，但是出现以下错误：

‘在不包含导航器的上下文中请求了导航器操作。用于从导航器推送或弹出路由的上下文必须是作为导航器小部件的后代的小部件的上下文。

这是更新的代码：

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:t2/helpers/currentuser.dart';

import 'screens/dashboard.dart';
import 'screens/login.dart';

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

CurrentUser user = new CurrentUser();

checkActiveUser(BuildContext context) async {
  SharedPreferences prefs = await SharedPreferences.getInstance();

try {
  user.usr = prefs.get('usr');
  user.pwd = prefs.get('pwd');

  if (user.usr.length == 0 && user.usr.length == 0) {
    user.isLoggedIn = false;
    Navigator
        .of(context)
        .pushNamedAndRemoveUntil('/dashboard', (Route<dynamic> route) => false);
  } else {
      throw new Exception('No user data found');
  }
} catch (e) {
    // Send to login screen
    user.isLoggedIn = false;
    Navigator
        .of(context)
        .pushNamedAndRemoveUntil('/login', (Route<dynamic> route) => false);
}

  /*
// How to read/write to local storage
int counter = (prefs.getInt('counter') ?? 0) + 1;
print('Pressed $counter times.');
prefs.setInt('counter', counter);
*/
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {
  void initState() {
    super.initState();
    checkActiveUser(context);
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('CADSYS'),
        ),
        body: new Center(
          child: new Text('Loading...'),
        ),
      ),
     routes: <String, WidgetBuilder> {
      '/dashboard': (BuildContext context) => new Dashboard(),
      '/login': (BuildContext context) => new Login()
    },
    );
  }
}