🐛 Null check operator used on a null value When using Combobox

[FengChendian]

Describe the bug
Here is exception
======== Exception caught by widgets library =======================================================
The following _CastError was thrown building Combobox(dirty, dependencies: [MediaQuery], state: _ComboboxState#57f33):
Null check operator used on a null value

The relevant error-causing widget was:
Combobox file:///C:/Users/FengChendian/Documents/Code/Android/serialport_tool/lib/UI_components/title_combo_menu.dart:81:28
When the exception was thrown, this was the stack:
#0 FluentTheme.of (package:fluent_ui/src/styles/theme.dart:25:70)
#1 _ComboboxState._textStyle (package:fluent_ui/src/controls/form/combo_box.dart:1181:35)
#2 _ComboboxState.build (package:fluent_ui/src/controls/form/combo_box.dart:1320:13)
#3 StatefulElement.build (package:flutter/src/widgets/framework.dart:4691:27)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574:15)

====================================================================================================
If I replace Combobox by dropdownButton, excetion will disappear.
My code is :

  final values = <String>['Blue', 'Green', 'Yellow', 'Red'];
  String? comboBoxValue;
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => ComboMenuDataManager(
          comboBoxValue: defaultItem ?? items[0], items: items),
      child: Container(
        margin: EdgeInsets.symmetric(vertical: 8, horizontal: 6),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Text(
              '$title:',
              style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
            ),
            SizedBox(
              width: 100,
              child: Container(
                padding: EdgeInsets.all(4),
                child: Consumer<ComboMenuDataManager>(
                  builder: (_, combo, __) => SizedBox(
                    width: 200,
                    child: Combobox<String>(
                      // header: 'Colors',
                      placeholder: Text('Selected list item'),
                      isExpanded: true,
                      items: values
                          .map((e) => ComboboxItem<String>(
                        value: e,
                        child: Text(e),
                      ))
                          .toList(),
                      value: comboBoxValue,
                      onChanged: (value) {
                        print(value);
                        // if (value != null) setState(() => comboBoxValue = value);
                      },
                    ),
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

In FluentTheme.of (package:fluent_ui/src/styles/theme.dart:25:70), I found error code:

  static ThemeData of(BuildContext context) {
    return context.dependOnInheritedWidgetOfExactType<_FluentTheme>()!.data;
  }

[bdlukaa]

Are you using the FluentApp??

[FengChendian]

Oh my god... I thought it was just a non-essential component about setting style. It works well after using FluentApp.

Maybe documention should emphasize using it😂
Thanks for help!

[bdlukaa]

Oh my god... I thought it was just a non-essential component about setting style.

Almost every widget provided by this lib uses FluentTheme.of(context). There must be a FluentApp or a FluentTheme above all these widgets.

[ntwarijoshua]

@bdlukaa Am mixing Material with Fluent be able to use some of the components in fluent. i have wrapped them with FluentTheme. but i still get this error ```The following _CastError was thrown building _TooltipOverlay(dirty):
Null check operator used on a null value

This is the code

fluent.FluentTheme(
data: fluent.ThemeData(),
child: fluent.Localizations(
locale: const fluent.Locale.fromSubtags(languageCode: 'en'),
delegates: const [
fluent.DefaultFluentLocalizations.delegate,
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate,
],
child: SizedBox(
```

      Any ideas?

[bdlukaa]

@ntwarijoshua I need more info about your issue! What version are you using? Can you share a reproducible snippet?