setState and emit doesn't work well together. Discovered non-stop/infinite when setState is called.

[Max Lam]

Hi,

I have encountered an issue with BlocBuilder build function keep being triggered infinitely when with setState being used.

I usually don't call setState when using Bloc. But can't stop other external dependant widgets from having setState called.

Here is a flutter project to re-produce this issue:
https://github.com/maxlam79/flutter_bloc_nonstop_investigate.

Any help is appreciated. Thank you.

[Jannik Norden]

For me, it seems that the infinite loop you have created is not related to bloc. Once emit is called, your code is equivalent to the following code:

class _MyHomePageState extends State<MyHomePage> {
  /// Flags & Attributes
  int _counter = 0;

  @override
  Widget build(BuildContext context) {
    _incrementCounter();
    return Scaffold(
      body: Text('$_counter'),
    );
  }

  void _incrementCounter() {
    WidgetsBinding.instance.addPostFrameCallback((_) {
      setState(() {
        _counter++;
      });
    });
  }
}

The _incrementCounter method will get triggered on each execution of the build method, and the build method will get called every time setState is called. So calling _incrementCounter causes an infinite loop.

[Max Lam]

Thanks for pointing this out Jannik. I guess I would just have find a better way to maneuver both the Bloc characteristic and the setState/build life cycle characteristic.