Crash when toggling loading state immediately from initState

[rockgecko-development]

Hi, thanks for the library!

If I have no await delay in between setting _loading to true and false, the component remains showing the loading spinner indefinitely. If I have a very short delay instead (eg 1-10 ms), the component crashes with:

======== Exception caught by widgets library =======================================================
The following assertion was thrown building _BodyBuilder:
Hide called, but not showing!
'package:declarative_refresh_indicator/declarative_refresh_indicator.dart':
Failed assertion: line 122 pos 12: '_showing'

Example:

@override
  void initState() {
    super.initState();
    _refresh();
  }
 void _refresh() async {
    setState(() => _loading = true);
    //wait anything under ~500ms, or have no `await` at all
    await Future<void>.delayed(Duration(milliseconds: 1));
    if (mounted) setState(() => _loading = false);
  }

This occurs if _refresh is called immediately from initState.

[hacker1024]

Sorry for the delay, I'll look into your PR in the next two weeks or so. Thanks!

[hacker1024]

Hi @rockgecko-development,
I apologise again for the wait - I've been pretty busy.

The problem here, as you may have identified, is that setState is being called before the internal post-frame callback that initialises the widget is executed. This results in a race condition where didUpdateWidget is being called with refreshing = false before the post-frame callback that shows the indicator does its job.

setState should not be called in initState. You can call _refresh for the first time in a post-frame callback as well. I will fix this in the example.

Is this still an issue when setState is not called in initState?

[hacker1024]

Closing as this issue appears not to occur when initState is used correctly.