CODEWITHSUNDEEP
flutterdartstream-builder
BIS Tech
BIS Tech

Reputation: 19444

FutureBuilder/StreamBuilder called unnecessary times when Navigator.push?

My FutureBuilder/StreamBuilder called unnecessary times when navigating using push. Is it possible to stop without change navigator.push?

 Stream<List<Categorie>> getFromBloc;

  @override
  void didChangeDependencies() {
    getFromBloc = getData();
    super.didChangeDependencies();
  }

inside state, outside build method

  Stream<List<Categorie>> getData()=>
     _categoryBloc.category;

build method

   StreamBuilder(
        stream: getFromBloc,//_categoryBloc.category,
        builder: (_, AsyncSnapshot<List<Categorie>> snapshot) {
          if (snapshot.data == null) {
               ...
          } else {
            ...
            GestureDetector(
              child:...,
              onTap:(){
              Navigator.of(context).pushNamed('/subCategory',arguments: Arguments(postModel: post));
              }
          }
        })

I added debug point inside streamBuilder. when navigating it's running multiple times.

Upvotes: 0

Views: 481

Answers (1)

Igor Kharakhordin
Igor Kharakhordin

Reputation: 9903

pushNamed is being called every time getFromBloc stream changes (gets new data). You shouldn't call it anywhere inside build function at all. You might want to do it like this:

getFromBloc.first.then((data) => Navigator.of(context).pushNamed('/subCategory',arguments: Arguments(postModel: post)))

For example, you can do it in initState. Callback will be executed only once after getFromBloc stream gets a new value.

UPD: I got you wrong. Every time you push a new route not just StreamBuilder gets rebuild, but every page on the stack rebuilds to update the back button. There's an issue for that.

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

In particular, routes will rebuild because their navigator state has changed so they might need to update how they draw back buttons and the like.

Upvotes: 1

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