[DropdownMenu] Improve document on how to reset selectedValue #177599
Description
Steps to reproduce
1 - Create a simple statefull home page;
2 - Add a DropdownMenu with some options;
3 - Inform initialSelection with a selectedValue;
4 - Create one button with a pressed function that should change the value of selectedValue for null;
5 - Select one item;
6 - Press the button;
OBS: I think that I know why it happens. I checked the DropdownMenu flutter implementation and I saw that in didUpdateWidget function do not implement something when widget.initialSelection is null, of course there is a check to see if oldWidget.initialSelection != widget.initialSelection but it is just trying to find the current option in the list and effective change the value if there is. Of course I don't know if there is a reason for it, I'm just wondering that maybe this function should check if initialSelection is null to clear the controller text;
Expected results
The expected results is clean the dropdown selection UI;
Actual results
Don't clean selection.
Code sample
Code sample
import 'package:flutter/material.dart';
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String? selectedValue1;
String? selectedValue2;
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Theme.of(context).colorScheme.inversePrimary,
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text('Welcome to Flutter!'),
const SizedBox(height: 20),
DropdownMenu<String>(
width: 200,
label: const Text('First Dropdown'),
onSelected: (String? value) {
setState(() {
selectedValue1 = value;
});
},
initialSelection: selectedValue1,
dropdownMenuEntries: const <DropdownMenuEntry<String>>[
DropdownMenuEntry<String>(value: 'option1', label: 'Option 1'),
DropdownMenuEntry<String>(value: 'option2', label: 'Option 2'),
DropdownMenuEntry<String>(value: 'option3', label: 'Option 3'),
],
),
const SizedBox(height: 20),
DropdownMenu<String>(
width: 200,
label: const Text('Second Dropdown'),
initialSelection: selectedValue2,
onSelected: (String? value) {
setState(() {
selectedValue2 = value;
});
},
dropdownMenuEntries: const <DropdownMenuEntry<String>>[
DropdownMenuEntry<String>(value: 'choice1', label: 'Choice 1'),
DropdownMenuEntry<String>(value: 'choice2', label: 'Choice 2'),
DropdownMenuEntry<String>(value: 'choice3', label: 'Choice 3'),
],
),
const SizedBox(height: 20),
ElevatedButton(
onPressed: () {
setState(() {
selectedValue2 = null;
});
},
child: const Text('Clear Second Dropdown'),
),
],
),
),
);
}
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Logs
Logs
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Doctor output
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[√] Flutter (Channel stable, 3.35.7, on Microsoft Windows [Version 10.0.22631.6060], locale en-US)
[√] Windows Version (11 Enterprise 64-bit, 23H2, 2009)
[√] Android toolchain - develop for Android devices (Android SDK version 36.0.0)
[√] Chrome - develop for the web
[√] Visual Studio - develop Windows apps (Visual Studio Professional 2022 17.13.3)
[√] Android Studio (version 2024.1)
[√] VS Code (version 1.105.1)
[√] Connected device (5 available)
[√] Network resources
• No issues found!