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Null check operator used on a null value from userProvider #12

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javaskrskr opened this issue Jul 23, 2022 · 38 comments
Open

Null check operator used on a null value from userProvider #12

javaskrskr opened this issue Jul 23, 2022 · 38 comments
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waiting Waiting for Response

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@javaskrskr
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Hello everyone, I am encountering the issue of null check, I followed the tutorial video, around 3:17:28, when I switched the networkImage with user.photoUrl:
image

The null check error was thrown from the userProvider, error message: Exception has occurred. _CastError (Null check operator used on a null value), my code of userProvider.dart:
image

I have already tried upgrading the pub version, or using the final Userprovider userprovider instead of User, the result is either showing nothing after pressing the upload icon, or throwing the error of: Exception has occurred. _CastError (Null check operator used on a null value).

I would like to know how to resolve it, Thanks!
@lomanu4
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lomanu4 commented Aug 2, 2022

you have solved it, if not, I'll tell you

@javaskrskr
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Author

you have solved it, if not, I'll tell you

Hello, I have not yet solving it, may I know the possible solutions?

@lomanu4
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lomanu4 commented Aug 2, 2022

add this in mobile screen
//model.User? user = Provider.of(context).getUser;

Text('${user!.email ?? null }')

in ResponsiveLayout check

@OverRide
void initState() {

super.initState();
addData();

}
addData()async {
UserProvider _userProvider = Provider.of(context,listen: false);
await _userProvider.refreshUser();
}

@bozhen-ahmed964
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can you be more specific please cos i have same issue
add this in mobile screen
//model.User? user = Provider.of(context).getUser;

Text('${user!.email ?? null }')

in where do you mean to add this line

@kerumy
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kerumy commented Sep 13, 2022

@bozhen-ahmed964

In my case, this code works for me.

↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓

model.User? user = Provider.of(context).getUser;
final isUserLogin = user?.username ?? false;
~
body: isUserLogin == false
? const Text('No User')
: Center(child: Text(user!.username))
~

@bozhen-ahmed964
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I would give it a try some of my friends told me that somethings wrong with the user model

@jammydman
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I am also struggling with the same error and can't see how to implement this code. Could you please show where in the code these lines should be added? Thank you

@jinosh05
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Hello there, the error was due to null-safety. Just remove the nullability in User? and add late keyword. Check my fork for more details

@jammydman
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jammydman commented Sep 24, 2022 •
edited
Loading

Thank you for your response, this fixed some of the issue. I am now getting a new error:

Exception caught by widgets library ═══════════════════════════════════
LateInitializationError: Field '_user@23046349' has not been initialized.
The relevant error-causing widget was
PostCard

Do you know how I can also fix this?

Thank you for your assistance

@jinosh05
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jinosh05 commented Sep 24, 2022 via email

@jinosh05
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jinosh05 commented Sep 25, 2022 via email

@jinosh05
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jinosh05 commented Sep 27, 2022 via email

@bozhen-ahmed964
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im not pretty sure if it LOL my Mac fooled my due to saved cache

@jinosh05
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jinosh05 commented Sep 27, 2022 via email

@RivaanRanawat
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Owner

In UserProvider class, add the following code:


UserProvider with ChangeNotifier {
User? _user;

final AuthMethods _authMethods = AuthMethods();

User? get getUser => _user;

Future<void> refreshUser() async {
User user = await _authMethods.getUserDetails();
_user = user;
notifyListeners();
}
}

The change that we have made here is set the getUser's data type as User? which means it is of the type User which can or cannot be null.

In the screen where you're getting this error, AddPostScreen or any other screen, add the following code in build function:

final User? user = Provider.of<UserProvider>(context).getUser;
return user == null
? const Center(
child: CircularProgressIndicator(
),)
: _file == null
? Center(...)

What we are doing here is basically getting the user from our Provider and now since we have updated the getUser to return a data type of User?, check if user == null, if it is then we show a loading indicator to avoid the red screen other wise we just follow the widget tree we have typed in the video tutorials.

Note: This is not just necessary for AddPostScreen class, you can use it any file's build function where you think you'll get this error.

@RivaanRanawat RivaanRanawat added the waiting Waiting for Response label Sep 28, 2022
@jinosh05
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jinosh05 commented Oct 11, 2022 via email

@pnaskardev
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Okay so now the screen keeps on loading

@RivaanRanawat
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Owner

Okay so now the screen keeps on loading

Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that.

@Abhay014
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Hello guys,
I am also facing the same error.
I even cleared my Firestore database + Firebase Auth Console. The screen keeps on loading

@Abhay014
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solved it. it was a spelling mistake in collection('users') I had written collection('user')

@FrancisIje
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Hello, I have cleared firestore database and firebase Auth and the screen keeps loading

@FrancisIje
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Okay so now the screen keeps on loading

Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that.

Mine didn't work after that

@jinosh05
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jinosh05 commented Dec 6, 2022

I think I have fixed the issue , check my latest commit and close this issue

@huutan3621
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Hi, I'm having the same issue. Has anyone solved the problem yet?

@utkarshshukla03
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Okay so now the screen keeps on loading

Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that.

Mine didn't work after that

Francislje did you resolved the error?

@FrancisIje
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FrancisIje commented Dec 14, 2022 via email

@huutan3621
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On Tue, Dec 13, 2022 at 12:05 PM utkarshshukla03 @.> wrote: Okay so now the screen keeps on loading Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that. Mine didn't work after that Francislje did you resolved the error? — Reply to this email directly, view it on GitHub <#12 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/APX3MROFWABBW2H6PARTIY3WNBKBNANCNFSM54OGGZ7Q . You are receiving this because you commented.Message ID: @.>
Yes I have solved this issue. Thanks

How did you solved this? Can I have your code to fix this?
Thank you so much

@utkarshshukla03
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On Tue, Dec 13, 2022 at 12:05 PM utkarshshukla03 @.> wrote: Okay so now the screen keeps on loading Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that. Mine didn't work after that Francislje did you resolved the error? — Reply to this email directly, view it on GitHub <#12 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/APX3MROFWABBW2H6PARTIY3WNBKBNANCNFSM54OGGZ7Q . You are receiving this because you commented.Message ID: @.>
Yes I have solved this issue. Thanks

Can you please share how you solved? It will be really helpful

@utkarshshukla03
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utkarshshukla03 commented Dec 22, 2022 •
edited
Loading

On Tue, Dec 13, 2022 at 12:05 PM utkarshshukla03 @.> wrote: Okay so now the screen keeps on loading Try clearing off your Firestore database + Firebase Auth Console and rechecking. Let me know if it works after that. Mine didn't work after that Francislje did you resolved the error? — Reply to this email directly, view it on GitHub <#12 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/APX3MROFWABBW2H6PARTIY3WNBKBNANCNFSM54OGGZ7Q . You are receiving this because you commented.Message ID: @.>
Yes I have solved this issue. Thanks

@FrancisIje
please reply, thanks

@FrancisIje
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To be very honest, I can't remember how cause I went through a lot of trials and errors

@utkarshshukla03
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@FrancisIje can you please share your code? It will be really helpful

@RivaanRanawat
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Everyone getting this error, please share your GitHub repository.

@RivaanRanawat RivaanRanawat mentioned this issue Jan 29, 2023
Closed
@muhammetaydinn
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Guys I think I solved. Model wasnt nullable .

jsontodart
replace this:
model/user.dart

import 'package:cloud_firestore/cloud_firestore.dart';

class User {
  String? email;
  String? username;
  String? uid;
  String? bio;
  String? photoUrl;
  List<dynamic>? followers;
  List<dynamic>? following;

  User(
      {this.email,
      this.username,
      this.uid,
      this.bio,
      this.photoUrl,
      this.followers,
      this.following});

  User.fromJson(Map<String, dynamic> json) {
    email = json['email'];
    username = json['username'];
    uid = json['uid'];
    bio = json['bio'];
    photoUrl = json['photoUrl'];
    followers = json['followers'];
    following = json['following'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = <String, dynamic>{};
    data['email'] = email;
    data['username'] = username;
    data['uid'] = uid;
    data['bio'] = bio;
    data['photoUrl'] = photoUrl;
    data['followers'] = followers;
    data['following'] = following;
    return data;
  }

  static User fromSnap(DocumentSnapshot snap) {
    var snapshot = snap.data() as Map<String, dynamic>;
    return User(
        email: snapshot["email"],
        username: snapshot["username"],
        uid: snapshot["uid"],
        bio: snapshot["bio"],
        photoUrl: snapshot["photoUrl"],
        followers: snapshot["followers"],
        following: snapshot["following"]);
  }
}

mobile_screen_layout.dart

Widget build(BuildContext context) {
    model.User? user = Provider.of<UserProvider>(context).getUser;
    return Scaffold(
      body: Center(
        child: Text(user?.username ?? "Loading"),
      ),
    );
  }

responsive.dart

 @override
  void initState() {
    super.initState();
    addData();
  }

  addData() async {
    UserProvider _userProvider =
        Provider.of<UserProvider>(context, listen: false);
    await _userProvider.refreshUser();
  }

user.provider.dart

User? get getUser => _user;

@Ultra-rrich
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@muhammetaydinn when I try your solution, it kind of works but the profile picture doesn't display.
Thanks for your input.

However, please kindly check with your code for the responsive.dart file.
It's not complete. Otherwise kindly advise accordingly. Thank you.

@Ultra-rrich
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In UserProvider class, add the following code:


UserProvider with ChangeNotifier {
User? _user;

final AuthMethods _authMethods = AuthMethods();

User? get getUser => _user;

Future<void> refreshUser() async {
User user = await _authMethods.getUserDetails();
_user = user;
notifyListeners();
}
}

The change that we have made here is set the getUser's data type as User? which means it is of the type User which can or cannot be null.

In the screen where you're getting this error, AddPostScreen or any other screen, add the following code in build function:

final User? user = Provider.of<UserProvider>(context).getUser;
return user == null
? const Center(
child: CircularProgressIndicator(
),)
: _file == null
? Center(...)

What we are doing here is basically getting the user from our Provider and now since we have updated the getUser to return a data type of User?, check if user == null, if it is then we show a loading indicator to avoid the red screen other wise we just follow the widget tree we have typed in the video tutorials.

Note: This is not just necessary for AddPostScreen class, you can use it any file's build function where you think you'll get this error.

Please @RivaanRanawat the screen keeps loading...?
Can you explain to as why we have to face this issue?

cos it's really delaying my progress!

@Ultra-rrich
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Everyone getting this error, please share your GitHub repository.

https://github.com/Ultra-rrich/Insta-Clone.git

this is mine. please help me solve the prooblem.

@muhammetaydinn
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I fix the problem with giving an error after click register without adding picture.

@dilipharish
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Guys I think I solved. Model wasnt nullable .

jsontodart replace this: model/user.dart

import 'package:cloud_firestore/cloud_firestore.dart';

class User {
  String? email;
  String? username;
  String? uid;
  String? bio;
  String? photoUrl;
  List<dynamic>? followers;
  List<dynamic>? following;

  User(
      {this.email,
      this.username,
      this.uid,
      this.bio,
      this.photoUrl,
      this.followers,
      this.following});

  User.fromJson(Map<String, dynamic> json) {
    email = json['email'];
    username = json['username'];
    uid = json['uid'];
    bio = json['bio'];
    photoUrl = json['photoUrl'];
    followers = json['followers'];
    following = json['following'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = <String, dynamic>{};
    data['email'] = email;
    data['username'] = username;
    data['uid'] = uid;
    data['bio'] = bio;
    data['photoUrl'] = photoUrl;
    data['followers'] = followers;
    data['following'] = following;
    return data;
  }

  static User fromSnap(DocumentSnapshot snap) {
    var snapshot = snap.data() as Map<String, dynamic>;
    return User(
        email: snapshot["email"],
        username: snapshot["username"],
        uid: snapshot["uid"],
        bio: snapshot["bio"],
        photoUrl: snapshot["photoUrl"],
        followers: snapshot["followers"],
        following: snapshot["following"]);
  }
}

mobile_screen_layout.dart

Widget build(BuildContext context) {
    model.User? user = Provider.of<UserProvider>(context).getUser;
    return Scaffold(
      body: Center(
        child: Text(user?.username ?? "Loading"),
      ),
    );
  }

responsive.dart

 @override
  void initState() {
    super.initState();
    addData();
  }

  addData() async {
    UserProvider _userProvider =
        Provider.of<UserProvider>(context, listen: false);
    await _userProvider.refreshUser();
  }

user.provider.dart

User? get getUser => _user;

Thanks a lot buddy,God Bless You

@Aishwarya2701 Aishwarya2701 mentioned this issue Oct 1, 2023
Open
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