Provider not found exception - firebase

Question

We have a cover page that has two buttons. One leads to the Contractor's login and registration page, and the other button leads to Hirer login and Registration.
In order to check whether a user is already logged into the app, we are using a wrapper.dart which contains the following code:
#override
Widget build(BuildContext context) {
final user = Provider.of<User>(context);
print(user);
enter code here
if (user == null) {
return Authenticate();
} else {
return Home();
}
}
}
This is our code snippet for contractorwrapper. We have a similar one for hirerWrapper as well. We are getting this error:
/flutter (23750): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (23750): The following ProviderNotFoundException was thrown building ContractorWrapper(dirty):
I/flutter (23750): Error: Could not find the correct Provider above this ContractorWrapper Widget

Answer 1

class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => User())],
child: MaterialApp(
home: Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("First appbar"),
),
body: Text("content")),
),
);
}
}

Answer 2

Assuming that the class User extends the class ChangeNotifier you have to add a ChangeNotifierProvider above your MaterialApp, which defines how the User is created.
Here you can find a great guide how to integrate the Provider into your app.
This would look like the following:
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider(
create: (context) => User(),
child: MaterialApp(
home: Scaffold(
appBar: AppBar(
backgroundColor: Colors.blue,
title: Text("First appbar"),
),
body: Text("content")),
),
);
}
}
//just an example
class User extends ChangeNotifier {
String _name;
set name(String value) {
_name = value;
notifyListeners();
}
String get name => _name;
}
If something is unclear - Feel free to ask.