How to reset value in Flutter DropdownButtonFormField

Question

I want to reset value at DropdownButtonFormField, value is changed to null, but DropdownButtonFormField doesn't change. Where is the problem? If I have used DropdownButton it was changing value properly, value was cleared. I need to use DropdownButtonFormField.

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {

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


class MyAppState extends State<MyApp> {

  String abc;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center (
          child: Column(
            children: <Widget>[DropdownButtonFormField(
              hint: Text('select value'),
              value: abc,
              items: <String>['A', 'B', 'C', 'D'].map((String value) {
                return DropdownMenuItem<String>(
                  value: value,
                  child: Text(value),
                );
              }).toList(),
              onChanged: (String newValue) {
                setState(() {
                  abc = newValue;
                });
              },
           ),
            Text("value is $abc"),
          ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: (){
            setState((){
              abc = null;
            });
         },
         tooltip: 'Reset',
         child: Icon(Icons.clear),
       )        
       ),
    );
  }
}

give the first value rather than null. In your case, that is "A" or assing " " — Abhishek Ghaskata, Apr 27 '20 at 16:19
It is not what I need... I know that there can be empty item.. It have to work that way, with DropdownButton it is possible... there isn't problem null value , on button press it cannot set any value from items. — Maroshb, Apr 27 '20 at 20:29
with DropDownButton it works as wrote .. but it has not some features as DropDownButtonFormField — Maroshb, Apr 29 '20 at 09:03
@Maroshb you found any solution with DropdownButtonFormField? — Krunal Darji, May 14 '20 at 16:28

score 19 · Accepted Answer · answered Sep 20 '20 at 09:28

You can use a GlobalKey<FormFieldState>.


class SomeWidget extends StatelessWidget {
  final GlobalKey<FormFieldState> _key;

  @override
  Widget build() {
    return DropdownButtonFormField(
      key: _key,
      //...
    )
  }

  reset() {
    _key.currentState.reset();
  }
}

https://dartpad.dev/04247868fa2e86c5f417532486b48870

score 6 · Answer 2 · answered Dec 30 '20 at 14:36

class SomeWidget extends StatelessWidget {
  final GlobalKey<FormFieldState> _key = GlobalKey<FormFieldState>();

  @override
  Widget build() {
    return DropdownButtonFormField(
      key: _key,
      //...
    )
  }

  reset() {
    _key.currentState.reset();
  }
}

score 0 · Answer 3 · edited Aug 15 '23 at 14:18

Have the key a defined in you controller as below:

GlobalKey<FormFieldState> productlistddlKey =GlobalKey<FormFieldState>();

Here how to reset inside the controller

productlistddlKey.currentState?.reset();

In the page, define your DropdownButtonFormField

   Obx(() =>  DropdownButtonFormField(
                      key: controller.productlistddlKey,
                    isDense: true,
                    autovalidateMode: AutovalidateMode.onUserInteraction,
                    decoration: const InputDecoration(
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.all(
                          Radius.circular(5),
                        ),
                      ),
                    ),
                    items: [],
                    value: value,
                    onChanged: (value) {
                    ///  
                    },
                    isExpanded: true,
                  ))

How to reset value in Flutter DropdownButtonFormField

3 Answers3

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