CODEWITHSUNDEEP
flutterdartriverpod
srihari ayapilla
srihari ayapilla

Reputation: 303

How to listen to a specific variable in flutter riverpod?

I have a 'homeScreenViewController' provider and it is a StateNotifierProvider. The state it provides is a class with multiple variables. I want my button widget to rebuild only when a particular variable 'isLoadMoreLoading' changes. But when I use like below everytime any variable is updated, my button rebuilds. How to achieve this? I am using flutter_riverpod: ^1.0.0.dev6

Consumer(
          builder: (context, ref, child) {
            var _isLoadMoreLoading = ref.watch(homeScreenViewController).isLoadMoreLoading;
            return Column(
              children: [
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    ElevatedButton(
                      onPressed: () async {
                        if (!_isLoadMoreLoading) {
                          await ref
                              .read(homeScreenViewController.notifier)
                              .loadMorePokemons();
                          WidgetsBinding.instance!
                              .addPostFrameCallback((_) {
                            _scrollController.animateTo(
                                _scrollController.position.maxScrollExtent,
                                duration: Duration(milliseconds: 100),
                                curve: Curves.easeInOut);
                          });
                        }
                      },
                      child: _isLoadMoreLoading
                          ? Container(
                              width: 50.0,
                              height: 1.0,
                              child: LinearProgressIndicator(
                                color: Colors.black,
                                minHeight: 1.0,
                              ),
                            )
                          : Text('Load More Pokemon'),
                    ),
                  ],
                )
              ],
            );
          },
        ),

Upvotes: 3

Views: 3432

Answers (1)

Moksh Mahajan
Moksh Mahajan

Reputation: 93

With the release of version 1.0.0, ref.watch now supports filtering rebuilts using myProvider.select((value) => ...)

If you have used flutter_bloc, we can say that it's riverpod equivalent of Bloc's buildWhen.

So, in your case we can do something like this:

var _isLoadMoreLoading = ref.watch(homeScreenViewController.select((viewController) => viewController.isLoadMoreLoading));

This will allow consumer widget to rebuilt only when isLoadMoreLoading variable updates its value.

Can be referred here: https://pub.dev/packages/riverpod/versions/1.0.0-dev.6/changelog

Upvotes: 5

Related Questions