local storage login & logout & auto login

 local storage login & logout & auto login:

code:

import 'package:flutter/material.dart';
	import 'package:shared_preferences/shared_preferences.dart';
	void main() => runApp(MyApp());
	class MyApp extends StatefulWidget {
	@override
	_MyAppState createState() => _MyAppState();
	}
	class _MyAppState extends State<MyApp> {
	@override
	Widget build(BuildContext context) {
	return MaterialApp(
	title: 'Auto Login',
	theme: ThemeData(
	primarySwatch: Colors.blue,
	),
	home: MyHomePage());
	}
	}
	class MyHomePage extends StatefulWidget {
	@override
	_MyHomePageState createState() => _MyHomePageState();
	}
	class _MyHomePageState extends State<MyHomePage> {
	TextEditingController nameController = TextEditingController();
	bool isLoggedIn = false;
	String name = '';
	@override
	void initState() {
	super.initState();
	autoLogIn();
	}
	void autoLogIn() async {
	final SharedPreferences prefs = await SharedPreferences.getInstance();
	final String userId = prefs.getString('username');
	if (userId != null) {
	setState(() {
	isLoggedIn = true;
	name = userId;
	});
	return;
	}
	}
	Future<Null> logout() async {
	final SharedPreferences prefs = await SharedPreferences.getInstance();
	prefs.setString('username', null);
	setState(() {
	name = '';
	isLoggedIn = false;
	});
	}
	Future<Null> loginUser() async {
	final SharedPreferences prefs = await SharedPreferences.getInstance();
	prefs.setString('username', nameController.text);
	setState(() {
	name = nameController.text;
	isLoggedIn = true;
	});
	nameController.clear();
	}
	@override
	Widget build(BuildContext context) {
	return Scaffold(
	appBar: AppBar(
	title: Text('Auto Login Home Page'),
	),
	body: Center(
	child: Column(
	mainAxisAlignment: MainAxisAlignment.center,
	children: <Widget>[
	!isLoggedIn ? TextField(
	textAlign: TextAlign.center,
	controller: nameController,
	decoration: InputDecoration(
	border: InputBorder.none, hintText: 'Please enter your name'),
	) : Text('You are logged in as $name'),
	SizedBox(height: 10.0),
	RaisedButton(
	onPressed: () {
	isLoggedIn ? logout() : loginUser();
	},
	child: isLoggedIn ? Text('Logout') : Text('Login'),
	)
	],
	),
	), // This trailing comma makes auto-formatting nicer for build methods.
	);
	}
	}