how can i change bool variable using Flutter Riverpod

Question

i am new to Flutter Riverpod management

i have stfl widget using Flutter Riverpod management, i need to change the test bool varible to true but cannot handle it

final testProvider = StateProvider<bool>((ref) => false);

`class FriendsList extends ConsumerStatefulWidget {


  const FriendsList({Key? key}) : super(key: key);

  @override
  _FriendsListState createState() => _FriendsListState();



}

class _FriendsListState extends ConsumerState<FriendsList> {







 @override
 Widget build(BuildContext context) {
 bool test = ref.watch(testProvider);
        return Stack( //edit
    children [
    !test ? Text('bool varible is false')
                         :  Text('bool varible is true')
     FutureBuilder(
           future: FirebaseFirestore.instance.collection('users')
                      .doc('userId').get(),
            builder: (context, AsyncSnapshot snapshot) {
               if(!snapshot.hasData){
                     return Text('');
                  }else{ 
                    
                        ref.read(testProvider.state).state = true;
                   }  
               return snapshot.data['name'];

i have no idea how to handle this . also i am not sure of my code if it right , and how to dispose it if it need to

Solution

The value in a Provider cannot be changed from outside the Provider. Use a StateProvider instead.

Check this out:

final testProvider = StateProvider<bool>((ref) => false);

class FriendList extends ConsumerStatefulWidget {
  const FriendList({Key? key}) : super(key: key);

  @override
  ConsumerState<ConsumerStatefulWidget> createState() => _FriendListState();
}

class _FriendListState extends ConsumerState<FriendList> {
  @override
  Widget build(BuildContext context) {
    bool test = ref.watch(testProvider);
    return IconButton(
      onPressed: () {
        ref.read(testProvider.state).state = true;
      },
      icon: Text(
        test ? "Variable updated" : "Still not updated",
      ),
    );
  }
}

Visit Riverpod documentation to learn more about it.

EDIT: I have written a complete example using Provider and StateNotifierProvider

A service to communicate with Firebase

class UserService {
  static Future<Map> getUser() async {
    DocumentSnapshot<Map> s = await FirebaseFirestore.instance
        .collection('users')
        .doc('userId')
        .get();
    return Map.from(s.data()!);
  }
}

A StateNotifierProvider and StateNotifier communicating with the service:

final userProvider = StateNotifierProvider<UserNotifier, AsyncValue<Map>>((ref) => UserNotifier());

class UserNotifier extends StateNotifier<AsyncValue<Map>> {
  UserNotifier() : super(AsyncLoading()) {
    get();
  }

  void get() async {
    state = AsyncData(await UserService.getUser());
  }
}

A testProvider

final testProvider = Provider<bool>((ref) {
  AsyncValue test = ref.watch(userProvider);
  return test is AsyncData;
});

And the Providers consumption

class FriendList extends ConsumerWidget {
  const FriendList({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    AsyncValue value = ref.read(userProvider);
    bool test = ref.read(testProvider);
    return Column(
      children: [
        Text(test ? "bool varialbe is true" : "bool varialbe is false"),
        value.when(
          loading: () => Text('Loading...'),
          data: (data) => Text('${data['name']}'),
          error: (error, __) => Text('Error: $error'),
        ),
      ],
    );
  }
}

Comments

[Nadia Yaseen]

thanks it work , but it give warning message setState() or markNeedsBuild() called during build. however i don't use setstate

[Josteve]

Hmm...It shouldn't, is this only place you used riverpod?

[Josteve]

Also, can you please accept and upvote?

[Nadia Yaseen]

no difference place , please take a look again since i edit the code , in the fact i was using setstate before , then someone give me tip to use riverpod instead so i can avoid this warning message of memory leak , but now it is the same message , it like disappointed, this is simple sample ,

[Nadia Yaseen]

oh it you the one who give me that tip , well , it's same Error :D

[Josteve]

Hey @NadiaYaseen check the edit.

[Nadia Yaseen]

same............

[Josteve]

Hey @NadiaYaseen, I've added the complete code for the entire thing with Riverpod.