DropdownButtonFormField is not re-rendered after value is changed programmatically

[lazarvgd]

I just created a simple app in order to see what am I doing wrong

The code:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  List<int> myList = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
  int currentNumber = 1;
  int anotherNumber = 9;

  void _incrementCounter() {
    setState(() {
      _counter++;
      anotherNumber = _counter;
      currentNumber = _counter;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            DropdownButtonFormField<int>(
              value: currentNumber,
              items: myList.map((int value) {
                return DropdownMenuItem<int>(
                  value: value,
                  child: Container(
                    width: 200,
                    child: Text(
                      value.toString(),
                    ),
                  ),
                );
              }).toList(),
              onChanged: (int newValue) {
                setState(() {
                  anotherNumber = newValue;
                  currentNumber = newValue;
                });
              },
            ),
            DropdownButtonFormField<int>(
              value: anotherNumber,
              items: myList.map((int value) {
                return DropdownMenuItem<int>(
                  value: value,
                  child: Container(
                    width: 200,
                    child: Text(
                      value.toString(),
                    ),
                  ),
                );
              }).toList(),
              onChanged: (int newValue) {
                setState(() {
                  anotherNumber = newValue;
                });
              },
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

The flutter doctor -v:

$ flutter doctor -v
[✓] Flutter (Channel stable, v1.17.0, on Mac OS X 10.15.4 19E287, locale en-RS)
    • Flutter version 1.17.0 at /Users/lazarjovicic/flutter
    • Framework revision e6b34c2b5c (9 days ago), 2020-05-02 11:39:18 -0700
    • Engine revision 540786dd51
    • Dart version 2.8.1

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/lazarjovicic/Library/Android/sdk
    • Platform android-29, build-tools 29.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.4.1, Build version 11E503a
    • CocoaPods version 1.8.4

[✓] Android Studio (version 3.6)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 45.1.1
    • Dart plugin version 192.7761
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] VS Code (version 1.44.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.10.1

[✓] Connected device (1 available)
    • SM G970F • RF8M728WTMP • android-arm64 • Android 10 (API 29)

• No issues found!

The demonstration with code above:
https://streamable.com/fwwd46
EDIT:
The Expectation:
Update the first dropdown filed -> the second dropdown field will be updated automatically

The Result:
Update the first dropdown field -> the second dropdown field remains unchanged.

Please let me know if you need additional information or any further explanation regarding the problem.

Thanks

[lazarvgd]

I check version 1.13.4 and this actually works

$ flutter doctor -v
[✓] Flutter (Channel unknown, v1.13.4, on Mac OS X 10.15.4 19E287, locale en-RS)
• Flutter version 1.13.4 at /Users/lazarjovicic/flutter
• Framework revision bd25f70 (5 months ago), 2019-12-19 09:45:02 -0800
• Engine revision 0f90e65
• Dart version 2.8.0 (build 2.8.0-dev.0.0 aa6709974d)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
• Android SDK at /Users/lazarjovicic/Library/Android/sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-29, build-tools 29.0.2
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.4.1, Build version 11E503a
• CocoaPods version 1.8.4

[✓] Android Studio (version 3.6)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 45.1.1
• Dart plugin version 192.7761
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] VS Code (version 1.44.2)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.10.1

[✓] Connected device (2 available)
• SM G970F • RF8M728WTMP • android-arm64 • Android 10 (API 29)
• iPhone 6 • B56B92F3-A2D9-4F91-A161-E2761F80C51C • ios • com.apple.CoreSimulator.SimRuntime.iOS-12-4 (simulator)

• No issues found!

[VladyslavBondarenko]

Reproduces with current dev 1.19.0-0.0.pre as well.
But yes, 1.13.4 is working as intended

[VladyslavBondarenko]

I changed the title, because new values are set by setState, but second DropdownButtonFormField is not updated

  @override
  Widget build(BuildContext context) {

    print(currentNumber);
    print(anotherNumber);

    return Scaffold(

[pedromassango]

DropdownButtonFormField widget is really using badly the value param. I just found a related issue here #56929

You can reproduce it by tapping FAB button 10 times using the example code in this issue!

[HansMuller]

CC @shihaohong

[jlubeck]

I can confirm @pedromassango PR fixes my issue: #57006
Pretty sure it fixes this one as well

[pedromassango]

Thanks. I'm just adding tests, before opening the PR for review

[pedromassango]

PR moved to #56898

[shihaohong]

I've marked this issue as a candidate for cherry-picking into the stable branch since this is a regression that has resulted in multiple open issues over the last few days (#57006, #56983, #57066) and revived an older DropdownButtonFormField issue (#27821 (comment)), presumably from devs trying to find an answer to their problem.

See https://github.com/flutter/flutter/wiki/Flutter-Cherrypick-Process for more information on how the process works.

[pedromassango]

@shihaohong Can you confirm that this is not a regretion too: #56365? Or it always behave that way?!

[shihaohong]

@pedromassango I don't know since I haven't looked at that issue yet. However, since that issue is unrelated to this one, let's discuss that one in #56365 and not here.

[jlubeck]

Maybe include the cp: 1.18 label as well??

[lazarvgd]

When we can expect this issue to be solved?
Thanks

[pedromassango]

This was already solved. We're just waiting to have it in the next Flutter beta release!

[lazarvgd]

This was already solved. We're just waiting to have it in the next Flutter beta release!

Sorry, I wasn't clear, when we can expect this issue to be in stable release?

thanks

[pedromassango]

Ok. Can take time for stable channel to be released. So if you really want this, you may want to use the beta channel, once this lands to beta

[lazarvgd]

Ok. Can take time for stable channel to be released. So if you really want this, you may want to use the beta channel, once this lands to beta

Thanks, but that is a bad idea for production app... thanks

[pedromassango]

Please note that I never know when a stable version will be released. I just say that because this PR is not even in a beta release, so it can take time to go to stable.

[pcsosinski]

@shihaohong which commit(s) are needed for the 1.17 branch if we cherrypick this?

[shihaohong]

@pcsosinski This is the commit needed for the cherrypick: 1aaf73f

[tvolkert]

eng approval for cp of #57037 into 1.17

[pedromassango]

@lazarvgd This has landed to 1.17.2

[pcsosinski]

removed 1.18 label as we're going to 1.19 for beta soon.

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.