How to add "this user/account does not exist" error in Flutter, using Firebase? - firebase

Question

I am trying to make a login page in Flutter. I have used Firebase as well for user authentication and logging in. The problem is, while I can login successfully with the correct information, I am unable to display anything like a pop up error box or message that the account does not exist. This is my code :
class _LoginPageState extends State<LoginPage> {
String _email, _password;
final auth = FirebaseAuth.instance;
bool hidepwd = true;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
brightness: Brightness.light,
backgroundColor: Colors.transparent,
elevation: 0,
leading: Container(
margin: EdgeInsets.all(5),
width: 50,
height: 50,
decoration: BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(10)),
color: Color(0xffe9eefa),
),
child: IconButton(
onPressed: (){Navigator.pop(context);},
icon: Icon(
Icons.keyboard_arrow_left_rounded,
color: Color(0xff2657ce),
),
),
),
),
body: ListView(
children: <Widget>[
Container(
child: IconButton(
icon: Icon(
Icons.account_circle_rounded,
color: Color(0xff2657ce),
size:100,
),
),
),
SizedBox(height: 50,),
Expanded(
child: Container(
padding: const EdgeInsets.symmetric(horizontal: 25.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Container(
padding: EdgeInsets.only(right: 240),
child: Text('Email Address', style: TextStyle(
fontSize: 15,),),
),
SizedBox(height: 10,),
Container(
padding: EdgeInsets.symmetric(vertical: 2, horizontal: 20),
decoration: BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(20)),
color: Colors.grey.withOpacity(0.2),
),
child: TextFormField(
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
hintText: 'Email',
),
onChanged: (value) {
setState(() {
_email = value.trim();
});
},
),
),
SizedBox(height: 20,),
Container(
padding: EdgeInsets.only(right: 270),
child: Text('Password', style: TextStyle(
fontSize: 15,
),),
),
SizedBox(height: 10,),
Container(
padding: EdgeInsets.symmetric(vertical: 2, horizontal: 20),
decoration: BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(20)),
color: Colors.grey.withOpacity(0.2),
),
child: Row(
children: <Widget>[
Expanded(
child: TextFormField(
obscureText: hidepwd,
decoration: InputDecoration(hintText: 'Password'),
onChanged: (value) {
setState(() {
_password = value.trim();
});
},
),
),
Container(
height: 50,
width: 50,
child: IconButton(
onPressed: togglepwdVisibility,
icon: IconButton(
icon: hidepwd == true ? Icon(
Icons.visibility_off
): Icon(Icons.visibility),
),
),
)
],
),
),
SizedBox(height: 20,),
RaisedButton(
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(15.0)),
color: Color(0xff5178D7),
child: Text("Log In", style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.w600,
fontSize: 15
),),
onPressed: (){
auth.signInWithEmailAndPassword(email: _email, password: _password).then((_){
Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (context) => frontpage()));
});
}
),
SizedBox(height: 20,),
Container(
child: Center(
child: Text('---- or ----'),
),
),
SizedBox(height: 20,),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("Don't have an account? "),
InkWell(
onTap: openSignUpPage,
child: Text("Sign Up", style: TextStyle(
color: Color(0xff1A3C90),
fontWeight: FontWeight.w700
),),
)
],
)
],
),
),
),
],
),
);
}
Any ideas/suggestions on what I could add or change in my code to have that error message included when I am unable to login overall?

Answer 1

In your login onPressed: (){ ... }, catch the FirebaseAuthException.
Source: https://firebase.flutter.dev/docs/auth/usage/#sign-in
try {
UserCredential userCredential = await FirebaseAuth.instance.signInWithEmailAndPassword(
email: "barry.allen#example.com",
password: "SuperSecretPassword!"
);
} on FirebaseAuthException catch (e) {
if (e.code == 'user-not-found') {
print('No user found for that email.');
} else if (e.code == 'wrong-password') {
print('Wrong password provided for that user.');
}
}

Answer 2

If you need alerts to pop on each login error you can try using the following function but only if you are using TextEdittingController:
signIn() async {
if (_loginFormKey.currentState!.validate()) {
_loginFormKey.currentState!.save();
try {
await FirebaseAuth.instance
.signInWithEmailAndPassword(
email: _emailController.text,
password: _passwordController.text)
.then((currentUser) => FirebaseFirestore.instance
.collection("users")
.doc(currentUser.user!.uid)
.get()
.then((conext) => Navigator.push(
context,
MaterialPageRoute(
builder: (context) => HomePage())))
.catchError((err) => print(err)));
} on FirebaseAuthException catch (error) {
if (error.code == 'user-not-found') {
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text("Auth Exception!"),
content: Text("This User Does Not Exist."),
actions: <Widget>[
Row(
children: [
ElevatedButton(
child: Text("Sign In Again"),
onPressed: () {
Navigator.of(context).pop();
},
),
],
)
],
);
});
} else if (error.code == 'wrong-password') {
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text("Auth Exception!"),
content: Text("The Password Entered is Invalid."),
actions: <Widget>[
Row(
children: [
ElevatedButton(
child: Text("Sign In Again"),
onPressed: () {
Navigator.of(context).pop();
},
),
],
)
],
);
});
}
}
}
}