第一种方法

在路由配置的时候应该有二个page配置

'/': (context) => HomePage(),
'/login': (context)  => LoginPage(),

main.dart中的初始化配置如下

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  isLogin = await obtionLoginData();//异步获取本地状态 值传到下面方法
  runApp(MyApp());
}

MaterialApp(
initialRoute: isLogin ? '/' : '/login'
onGenerateInitialRoutes: (name) {//必须实现 不然会先加载'/'页面才会加载'/login'页面
    return [MaterialPageRoute(builder: (context){
       return LoginPage();
      })]
 }
)

第二种方法

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

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  Future<String> obtionSharedPrefs() async {//异步获取本地数据
    SharedPreferences prefs = await SharedPreferences.getInstance();
    phone  = prefs.getString('phone') ?? '';
    return phone;
  }
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: FutureBuilder<String>(
        future: obtionSharedPrefs(),
        builder: (BuildContext context,AsyncSnapshot<String> snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return CircularProgressIndicator();//加载中
          } else if (snapshot.connectionState == ConnectionState.done) {//加载完成
            if (snapshot.hasError) {
              return const Text('Error');
            } else if (snapshot.hasData && snapshot.data.isNotEmpty) {
              return Home();//已经登录过 直接进入首页
            } else {
              return Login();//没有登录过 进入登录页面
            }
          } else {//异常
            return Text('State: ${snapshot.connectionState}');
          }
        },
      ),
    );
  }
}

第三种方法

使用getx框架中的路由middlewares配置实现

///路由配置
class AppPage {
  static final routes = [
    GetPage(name: "/", page: ()=> const LoginPage(), middlewares: [AppMiddleware()),
    GetPage(name: "/login", page: ()=> const HomePage()]),
  ];
}

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await AppTool.initializeApp();;//异步初始化数据 加载sdk
  runApp(MyApp());
}
return GetMaterialApp(
   initialRoute: "/",
   getPages: AppPage.routes,
);

/*登录中间件*/
class AppMiddleware extends GetMiddleware {
  @override // 优先级越低越先执行
  int? get priority => -1;
  @override
  RouteSettings? redirect(String? route)  {
    final accessToken = UserSinglen().accessToken;//获取token 如果token没值就进入登录页面
    return accessToken == null ? const RouteSettings(name:'/login') : null;
  }
}