How to use shared preferences to keep user logged in flutter?

You can navigate to the Login page if the user details are saved in the storage else to the Home page with the below code

  Future<void> main() async {
      WidgetsFlutterBinding.ensureInitialized();
      SharedPreferences prefs = await SharedPreferences.getInstance();
      var email = prefs.getString('email');
      print(email);
      runApp(MaterialApp(home: email == null ? Login() : Home()));
    }

Save the required user details after the successful login

class Login extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () async {
            //after the login REST api call && response code ==200
            SharedPreferences prefs = await SharedPreferences.getInstance();
            prefs.setString('email', '[email protected]');
            Navigator.pushReplacement(context,
                MaterialPageRoute(builder: (BuildContext ctx) => Home()));
          },
          child: Text('Login'),
        ),
      ),
    );
  }
}

clear the details on logout

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: () async {
            SharedPreferences prefs = await SharedPreferences.getInstance();
            prefs.remove('email');
            Navigator.pushReplacement(context,
                MaterialPageRoute(builder: (BuildContext ctx) => Login()));
          },
          child: Text('Logout'),
        ),
      ),
    );
  }
}

Hope it helps!

Make sure WidgetFlutterBinding.ensureInitialized() is the first line of main()

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

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SharedPreferences prefs = await SharedPreferences.getInstance();
  bool login = prefs.getBool("login");
  print("login:" + login.toString());
  runApp(MaterialApp(home: login == null ? LoginPage(title: 'My App') : HomePage()));
}

class LoginPage extends StatelessWidget { ...