Authentication 如何在Flatter应用程序的入口点检查身份验证令牌

我需要知道如何在应用程序的入口点检查令牌。我已经将其保存在共享首选项中`

_saveToken() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    String token = await response.data['token'];
    await prefs.setString('jwt', token);
  }

---

`如果这个jwt不是null，我需要绕过我的登录屏幕。我该怎么做呢？

如果你有一个启动屏幕，你应该创建一个如下的函数并在initState中调用

---

这对我很有用。

如果你有一个启动屏幕，你应该创建一个如下的函数并在initState中调用

---

这对我有用。

您可以复制下面的粘贴运行完整代码 您可以在main中获取jwt令牌，并在initialRoute中检查jwt内容是否为null

代码片段

String jwt;

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();
  jwt = await prefs.getString("jwt");
  print('jwt ${jwt}');
  runApp(MyApp());
}
...
return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: jwt == null ? "login" : "/",
      routes: {
        '/': (context) => MyHomePage(
              title: "demo",
            ),
        "login": (context) => LoginScreen(),
      },

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/services.dart';

String jwt;

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();
  jwt = await prefs.getString("jwt");  
  print('jwt ${jwt}');
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: jwt == null ? "login" : "/",
      routes: {
        '/': (context) => MyHomePage(
              title: "demo",
            ),
        "login": (context) => LoginScreen(),
      },
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

class LoginScreen extends StatefulWidget {
  @override
  _LoginScreenState createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Login"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'This is Login screen',
            ),
          ],
        ),
      ),
    );
  }
}

---

您可以复制粘贴运行下面的完整代码 您可以在main中获取jwt令牌，并在initialRoute中检查jwt内容是否为null

代码片段

String jwt;

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();
  jwt = await prefs.getString("jwt");
  print('jwt ${jwt}');
  runApp(MyApp());
}
...
return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: jwt == null ? "login" : "/",
      routes: {
        '/': (context) => MyHomePage(
              title: "demo",
            ),
        "login": (context) => LoginScreen(),
      },

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/services.dart';

String jwt;

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  SharedPreferences prefs = await SharedPreferences.getInstance();
  jwt = await prefs.getString("jwt");  
  print('jwt ${jwt}');
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: jwt == null ? "login" : "/",
      routes: {
        '/': (context) => MyHomePage(
              title: "demo",
            ),
        "login": (context) => LoginScreen(),
      },
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

class LoginScreen extends StatefulWidget {
  @override
  _LoginScreenState createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Login"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'This is Login screen',
            ),
          ],
        ),
      ),
    );
  }
}

---

你能补充更多关于你的起始结构的细节吗。您首先显示的屏幕。启动屏幕是最好的选择，你可以添加更多关于你的启动结构的细节。您首先显示的屏幕。闪屏是最好的选择