CODEWITHSUNDEEP
flutter
Thomas B
Thomas B

Reputation: 65

Flutter DropdownButton dont show value, when using hint

i have an AlertDialog and want to use a DropdownButton for changing a value. At first there should be the hint visible. After choosing a value, the value should be visible. But when i use the hint, it never shows the value and vice versa.

DropdownButton(
     items: <String>['team1','team2'].map((String val) => DropdownMenuItem<String>(
    value: val,
    child: Text(val),
   )).toList(),
  //value: 'team1',
    hint: Text('Enter team'),
    
    onChanged: (value) {
      teteam.text = value;
    }
                ),

It has the correct function, but visibility isnt quite like i expect.

Upvotes: 4

Views: 2620

Answers (2)

petras J
petras J

Reputation: 2744

I'm posting a fully working code at the bottom

For future projects in order to 'activate the hint' ability you have to meet two conditions:

Set the initial value to null and the dropdown is enabled( list of strings and onChanged are non-null. Or so the official documentation says so.

Code below:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

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

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  String? theTeam = null;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: DropdownButton(
          value: theTeam,
          items: <String>['team1', 'team2']
              .map((String val) => DropdownMenuItem<String>(
                    value: val,
                    child: Text(val),
                  ))
              .toList(),
          hint: Text('Enter team'),
          onChanged: (String? value) {
            setState(() {
              theTeam = value!;
            });
          },
        ),
      ),
    );
  }
}

enter image description here

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Upvotes: 2

Marcel Dz
Marcel Dz

Reputation: 2714

You have to use setState since you want to change the UI of your app. Simply change the onchanged

onChanged: (value) {
              setState(() {
                teteam.text = value;
              });
            },
..

Working example right here: https://www.developerlibs.com/2019/09/flutter-drop-down-menu-list-example.html

setState from library: https://api.flutter.dev/flutter/widgets/State/setState.html

EDIT:

I assume you are trying to use setState in a stateless widget, which is immutable(unable to change).

Use a stateful widget to do so, like this:

class AddTodoDialog extends StatefulWidget{
  AddTodoDialog createState()=> AddTodoDialog();
}

class AddTodoDialog extends State<AddTodoDialog>{
 //Your code here
}

Upvotes: 0

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