Undefined name 'FirebaseAuth' - flutter

Question

The FirebaseAuth was working fine for me a few hours back but now I am receiving an error as :
Undefinded name 'FirebaseAuth' .I am unable to resolve it. Don't know what is the real issue. Would be a great help for me if anybody could step in and provide me a or more solutions.
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:jiwdopani/UserLogIn/MenuUse.dart';
import 'package:jiwdopani/services/error_handler.dart';
import 'package:jiwdopani/UserLogIn/login_page.dart';
class AuthService {
handleAuth() {
return StreamBuilder(
stream: FirebaseAuth.instance.authStateChanges(),
builder: (BuildContext context, snapshot) {
if (snapshot.hasData) {
return UserMenu();
} else
return LoginPage();
});
}
//Sign out
signOut() async {
try {
return await FirebaseAuth.instance.signOut();
}
catch(e){
print(e.toString());
return null;
}
}
//Sign In
signIn(String email, String password, context) {
FirebaseAuth.instance
.signInWithEmailAndPassword(email: email, password: password)
.then((val) {
UserMenu();
}).catchError((e) {
ErrorHandler().errorDialog(context, e);
});
}
//Signup a new user
signUp(String email, String password) {
return FirebaseAuth.instance
.createUserWithEmailAndPassword(email: email, password: password);
}
//Reset Password
resetPasswordLink(String email) {
FirebaseAuth.instance.sendPasswordResetEmail(email: email);
}

Answer 1

I fixed some of your code by adding types to the functions:
class AuthService {
Widget handleAuth() {
return StreamBuilder(
stream: FirebaseAuth.instance.authStateChanges(),
builder: (BuildContext context, snapshot) {
if (snapshot.hasData) {
return Container(); //change it back to your widget
} else
return Container();//change it back to your widget
});
}
//Sign out
void signOut() async {
try {
return await FirebaseAuth.instance.signOut();
} catch (e) {
print(e.toString());
return null;
}
}
//Sign In
void signIn(String email, String password, BuildContext context) {
FirebaseAuth.instance
.signInWithEmailAndPassword(email: email, password: password)
.then((val) {
return Container();
});
}
//Signup a new user
Future<UserCredential> signUp(String email, String password) async {
return await FirebaseAuth.instance
.createUserWithEmailAndPassword(email: email, password: password);
}
//Reset Password
void resetPasswordLink(String email) {
FirebaseAuth.instance.sendPasswordResetEmail(email: email);
}
}
Anyway, I think it's best not to have Widgets or UI in Auth Class, it is always better to separate UI from logic.