How to handle Flutter widget rebuilding with BLOC?

In regards to Flutter's way to rebuild widgets when navigating between routes, there is this issue: Pages on Navigator stack rebuild when a new page is pushed where the dev team and others provided these interesting insights:

1. About this reported behavior in the issue itself:

This is working as intended. In general, you should assume that all widgets can rebuild at any time, flutter error that they don't is mostly just an optimization. [...]

2. Further (re)explained here:

You should generally assume that every widget will be rebuilt flutter error every frame, and design your build methods to be idempotent [...]

3. When asked how to handle fetching data in build(context):

you'll need to restructure your code so that the data is not fetched again [...].

---

I am using BLoC to fetch remote data. For example, in my HomePage:

class HomeScreen extends StatelessWidget {   const HomeScreen({Key? key}) : super(key: key);    @override   Widget build(BuildContext context) {     return BlocBuilder<HomeBloc, HomeState>(       bloc: sl.get()..add(const GetHomeEvent()), // `sl` from package `GetIt`, a dependency injector       builder: (context, state) {         return AnimatedSwitcher(           duration: const Duration(milliseconds: 300),           child: state.join(             (initial) => const EmptyHome(),             (loading) => const LoadingHome(),             (success) => LoadedHome(homeEntity: success.homeEntity),             (failure) => FailedHome(errorMessage: failure.message),           ),         );       },     );   } 

As you can read, I build a BlocBuilder and upon its instantiation, I asked the HomeBloc to fetch data:

HomeBloc() : super(HomeState.initial()) {   on<GetHomeEvent>((event, emit) async {      print('load home event request');      // code to load home and notify of result via `emit()`     );   }); 

The log load home event request gets printed multiple times as I navigate in and out from my home page.

How should I go about and prevent unnecessarily reloading the home ?

• Should I simply cache it via a local variable?
• How to handle refresh properly (e.g. hit F5 in the web browser)?

9codings

15

Answers 1: of How to handle Flutter widget rebuilding with BLOC?

2023-06-09T10:36:18+00:00 2023-06-09T10:36:18+00:00 Answer Link