Assertion Error with useExpansionTileController

[kovaccc]

Assertion Error with useExpansionTileController

[rrousselGit]

The issue is most definitely unrelated to hooks. The controller was correctly created, and the error isn't thrown by flutter_hooks but Flutter.
My guess is that you're trying to use the controller before it is associated with a widget, and therefore trigger this assert.

Also note that your controller isn't listened. So your UI won't update when the value changes.

Two things:

• Consider raising an issue on the Flutter repo to have them improve their error message
• Try wrapping your leading in a builder, such as HooKBuilder or ValueListenableBuilder.
  This would delay the isExpanded usage to a point where the controller is linked with a widget

  leading: HookBuilder(
    builder: (context) {
      useListenable(expansionTileController);
      return  expansionTileController.isExpanded
            ? Assets.icons.minus.svg()
            : Assets.icons.plus.svg()
    },

[kovaccc]

Firstly, thank you for the prompt response and your suggestions. I understand your point that the issue might be due to the ExpansionTileController being used before it's associated with a widget and the controller not being listened to.

Following your advice, I attempted to use HookBuilder along with useListenable for the ExpansionTileController. However, I've run into a type inference issue. When I use useListenable with ExpansionTileController, I encounter the following error:

Couldn't infer type parameter 'T'.
Tried to infer 'ExpansionTileController' for 'T' which doesn't work:
  Type parameter 'T' is declared to extend 'Listenable?' producing 'Listenable?'.
  The type 'ExpansionTileController' was inferred from:
  Parameter 'listenable' declared as 'T' but argument is 'ExpansionTileController'.
Consider passing explicit type argument(s) to the generic.

This seems to suggest a type mismatch between ExpansionTileController and Listenable?, which useListenable expects.

Is there a workaround or a different approach you would recommend for ensuring that the ExpansionTileController is correctly used and listened to within the context of flutter_hooks? Any further guidance would be greatly appreciated. Thank you for your time and help.

[rrousselGit]

My bad, it's looking like ExpansionTileController isn't a Listenable.

Looks like you have to use ExpansionTileController.of instead;

leading: Builder(
  builder: (context) {
    final controller = ExpansionTileController.of(context);
    return  expansionTileController.isExpanded
          ? Assets.icons.minus.svg()
          : Assets.icons.plus.svg()
  },

[kovaccc]

No worries. I tried do it your way, it does not throw the error but also not changing the icon

class CustomExpansionTile extends HookWidget {
  final String title;
  final List<Widget> children;
  final EdgeInsets? tilePadding;
  final bool showDivider;

  const CustomExpansionTile({
    required this.title,
    required this.children,
    this.tilePadding,
    this.showDivider = true,
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    final expansionTileController = useExpansionTileController();
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: [
        Theme(
          data: Theme.of(context).copyWith(dividerColor: Colors.transparent),
          child: ExpansionTile(
            controller: expansionTileController,
            tilePadding: tilePadding,
            expandedAlignment: Alignment.topLeft,
            expandedCrossAxisAlignment: CrossAxisAlignment.start,
            trailing: HookBuilder(
              builder: (context) {
                return expansionTileController.isExpanded
                    ? Assets.icons.minus.svg()
                    : Assets.icons.plus.svg();
              },
            ),
            title: Text(
              title,
              style: context.appTextStyles.paragraph2SemiBold,
            ),
            children: children,
          ),
        ),
        if (showDivider) const CustomDivider(),
      ],
    );
  }
}

I will stick to useState instead.

  @override
  Widget build(BuildContext context) {
    final isExpanded = useState(false);
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: [
        Theme(
          data: Theme.of(context).copyWith(dividerColor: Colors.transparent),
          child: ExpansionTile(
            tilePadding: tilePadding,
            expandedAlignment: Alignment.topLeft,
            expandedCrossAxisAlignment: CrossAxisAlignment.start,
            trailing: isExpanded.value
                ? Assets.icons.minus.svg()
                : Assets.icons.plus.svg(),
            title: Text(
              title,
              style: context.appTextStyles.paragraph2SemiBold,
            ),
            onExpansionChanged: (bool expanded) => isExpanded.value = expanded,
            children: children,
          ),
        ),
        if (showDivider) const CustomDivider(),
      ],
    );
  }

[rrousselGit]

It's ultimately still unrelated to flutter_hooks. So I'd redirect you to Reddit/StackOverflow/Discord for further help requests :)