[FormBuilderDropdown]: <If onChanged Function is added, the FormBuilderDropdown stop working>

[CarmonaCarlos]

Is there an existing issue for this?

• I have searched the existing issues

Package/Plugin version

9.0.0

Flutter doctor

Flutter doctor

[√] Flutter (Channel stable, 3.10.0, on Microsoft Windows [Version 10.0.22621.1702], locale es-MX)
• Flutter version 3.10.0 on channel stable at C:\Users\Carlos\flutter_sdk\flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 84a1e904f4 (6 days ago), 2023-05-09 07:41:44 -0700
• Engine revision d44b5a94c9
• Dart version 3.0.0
• DevTools version 2.23.1

[√] Windows Version (Installed version of Windows is version 10 or higher)

[√] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
• Android SDK at C:\Users\Carlos\AppData\Local\Android\sdk
• Platform android-33, build-tools 31.0.0
• Java binary at: C:\Program Files\Android\Android Studio\jbr\bin\java
• Java version OpenJDK Runtime Environment (build 17.0.6+0-b2043.56-9586694)
• All Android licenses accepted.

[√] Chrome - develop for the web
• Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2022 17.5.5)
• Visual Studio at C:\Program Files\Microsoft Visual Studio\2022\Community
• Visual Studio Community 2022 version 17.5.33627.172
• Windows 10 SDK version 10.0.22621.0

[√] Android Studio (version 2022.2)
• Android Studio at C:\Program Files\Android\Android Studio
• Flutter plugin can be installed from:
https://plugins.jetbrains.com/plugin/9212-flutter
• Dart plugin can be installed from:
https://plugins.jetbrains.com/plugin/6351-dart
• Java version OpenJDK Runtime Environment (build 17.0.6+0-b2043.56-9586694)

[√] VS Code (version 1.78.2)
• VS Code at C:\Users\Carlos\AppData\Local\Programs\Microsoft VS Code
• Flutter extension version 3.64.0

[√] Connected device (3 available)
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.22621.1702]
• Chrome (web) • chrome • web-javascript • Google Chrome 113.0.5672.93
• Edge (web) • edge • web-javascript • Microsoft Edge 113.0.1774.42

[√] Network resources
• All expected network resources are available.

• No issues found!

Minimal code example

Code sample

import 'package:flutter/material.dart';
import 'package:flutter_form_builder/flutter_form_builder.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'package:form_builder_validators/form_builder_validators.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Flutter FormBuilder Demo',
      debugShowCheckedModeBanner: false,
      localizationsDelegates: [
        FormBuilderLocalizations.delegate,
        ...GlobalMaterialLocalizations.delegates,
        GlobalWidgetsLocalizations.delegate,
      ],
      supportedLocales: FormBuilderLocalizations.supportedLocales,
      home: Example(),
    );
  }
}

class Example extends StatefulWidget {
  const Example({Key? key}) : super(key: key);

  @override
  State<Example> createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
  int? selectedLineId;
  final GlobalKey<FormBuilderState> _formKey = GlobalKey<FormBuilderState>();
  late List<Line> lines;

  @override
  void initState() {
    lines = _initLines();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Example')),
      body: FormBuilder(
        key: _formKey,
        child: Column(
          children: <Widget>[
            FormBuilderDropdown<int>(
              name: 'lineId',
              valueTransformer: (int? val) => val?.toInt(),
              decoration: const InputDecoration(
                  labelText: 'lines', icon: Icon(Icons.ad_units)),
              validator: FormBuilderValidators.compose(
                  [FormBuilderValidators.required()]),
              items: lines
                  .map((Line item) => DropdownMenuItem<int>(
                        value: item.id,
                        child: Text(item.name),
                      ))
                  .toList(),
              onChanged: (int? value) {
                setState(() {
                  selectedLineId = value;
                });
              },
            )
          ],
        ),
      ),
    );
  }

  List<Line> _initLines() {
    //This is just for test purpose
    return <Line>[
      Line(
        id: 1,
        name: 'Test',
      ),
      Line(
        id: 2,
        name: 'Test 2',
      )
    ];
  }
}

class Line {
  final int id;
  final String name;

  Line({required this.id, required this.name});
}

Current Behavior

If I add setState inside of onChanged the FormBuilderDropdown is not working correctly:

If I select an option:

Then nothing is selected:

On previous version it was working once I update to 9.0.0 it stop to works.

Expected Behavior

If I select an option

For example:

Then the option is selected:

Steps To Reproduce

1. Add setState to onChanged

Aditional information

No response

[bull-xu]

The setState triggers the rebuild. and a break point to the didUpdateWidget showing the initialValue has been set to value:

To fix the issue, a walkaround is to set the items at initState.

[deandreamatias]

I test the example code on web with Flutter 3.10 and works fine. Please edit minimal example code or add more details about the bug

[eaedev]

Same problem here. If you use a setState in onChanged, then the widget get rebuilds and it jumps to the initial value

[tetious]

@deandreamatias I think the key here is that the form needs to rebuild to trigger. It probably won't happen as easily on the web, but on mobile the widget rebuilds when the input/keyboard changes, and that is pretty common on a form.

If you pick something in the dropdown (keyboard goes away) and then move focus to a widget that reopens the keyboard, the selected item dissapears.

[GiuseppeSperanza]

Yes, same problem. Any update?

[mngphm]

same problem, will this be fixed? or any workaround?

[tetious]

My workaround (which may not be the best, but seems to work) is to set the model prop value manually in onChanged, kinda like this:

onChanged: (value) => YOUR_MODEL.whateverProp = value,

[ncuillery]

More generally, rebuilding the widget where the FormBuilderDropdown is declared causes the following error if the items prop is reassigned:

The following assertion was thrown building MyForm:
setState() or markNeedsBuild() called during build.

This Form widget cannot be marked as needing to build because the framework is already in the process of building widgets. A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.

The workaround consists in keeping the items array (the same reference) by declaring the array of DropdownMenuItem in the initState, like @bull-xu mentioned for instance

[Dubemtopsite]

Facing same issue while using setState to update some variables from onChanged

[Dubemtopsite]

My workaround (which may not be the best, but seems to work) is to set the model prop value manually in onChanged, kinda like this:

onChanged: (value) => YOUR_MODEL.whateverProp = value,

Had to create a model for my form and update the model from the onChanged function

[hallmayer]

Same here.
Any update?

[godofsleepy]

Screen.Recording.2023-06-20.at.11.26.36.mov

Version 9.0.0
Got same error when on change trigger GetX builder(form key.did change -> getx).
then when i downgrade to version 8.0.0 its fixed, any suggest ?