The provider in flutter doesn't change a screens - flutter

Question

I'm using a provider in flutter app to change screens in my app. Here is my main.dart file:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/services/auth_service.dart';
import 'package:school_app/wrapper.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (_) => AuthService().auth,
child: MaterialApp(
home: Wrapper(),
),
);
}
}
Also this is my wrapper.dart file where the screens choose:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:school_app/screens/authenticate/auth.dart';
import 'package:school_app/models/user.dart';
import 'package:school_app/screens/school/home.dart';
import 'package:school_app/services/auth_service.dart';
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = Provider.of<AuthProvider>(context);
print(user.auth);
if(!user.auth) return Auth();
return Home();
}
}
And it is my AuthProvider class:
import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
class AuthService {
/* AuthUser _user(User user) {
return user != null ? AuthUser(uid: user.uid) : null;
}*/
AuthProvider auth = new AuthProvider();
//sign in
Future signIn(String username, String password) async {
try {
SharedPreferences prefs = await SharedPreferences.getInstance();
var dio = Dio();
Response user = await dio.post('url', data: {
'username': username,
'password': password
});
if(user.data['success'] == false) return user.data['msg'];
await prefs.setString('token', user.data['token']);
auth.setAuth(true);
print("SUCCESS");
} catch(e) {
print('Error ' + e.toString());
}
}
}
class AuthProvider with ChangeNotifier {
bool _auth;
AuthProvider() {
_auth = false;
}
bool get auth => _auth;
void setAuth(bool auth) {
_auth = auth;
notifyListeners();
}
}
Also I made this variants of Wrapper widget, but it didn't work also:
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = context.watch<AuthProvider>();
print(user.auth);
if(!user.auth) return Auth();
return Home();
}
}
And this one:
class Wrapper extends StatelessWidget {
#override
Widget build(BuildContext context) {
final user = context.watch<AuthProvider>();
print(user.auth);
if(!user.auth) return Auth();
return Home();
}
}
And when I call a function in AuthProvider class setAuth, nothing changed. Can you help me and find my mistake?