更改 DropDownButton 时如何更改变量

Question

I have 3 variables containing text that I can pass to message .

String easyDrop = 'All ok';
String mediumDrop = '1 problem';
String hardDrop = 'All not ok';

message: easyDrop ,

I would like to change them depending on the state of my DropDownButton. How can I do this?

import 'package:flutter/material.dart';

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

  @override
  State<DropDownButtonDifficultySettingsWidget> createState() => _DropDownButtonDifficultySettingsState();
}

class _DropDownButtonDifficultySettingsState extends State<DropDownButtonDifficultySettingsWidget> {
  String dropdownValue = 'Medium';

  @override
  Widget build(BuildContext context) {
    return Theme(
      data: ThemeData(
       splashColor: Colors.blue.withOpacity(0.4),),
      child: DropdownButton<String>(
        value: dropdownValue,
        elevation: 8,
        alignment: Alignment.centerRight,
        iconDisabledColor: Colors.blue,
        iconEnabledColor: Colors.blue,
        underline: Container(
             height: 0,
        ),
        style: const TextStyle(color: Colors.blue, fontWeight: FontWeight.w500, ),
        onChanged: (String? newValue) {
          
          setState(() {
            dropdownValue = newValue!;
          });
        },
        items: <String>['Easy', 'Medium', 'Hard']
            .map<DropdownMenuItem<String>>((String value) {
          return DropdownMenuItem<String>(
            value: value,
            child: Text(value),
          );
        }).toList(),
      ),
    );
  }
}

Answer 1

You can include a callback method to get selected item from DropDownButtonDifficultySettingsWidget

class DropDownButtonDifficultySettingsWidget extends StatefulWidget {
  final Function(String? selectedValue) callback;
  const DropDownButtonDifficultySettingsWidget(
      {Key? key, required this.callback})
      : super(key: key);

  @override
  State<DropDownButtonDifficultySettingsWidget> createState() =>
      _DropDownButtonDifficultySettingsState();
}

And on changed

onChanged: (String? newValue) {
  setState(() {
    dropdownValue = newValue!;
  });
  widget.callback(dropdownValue); //this
},

Now when ever you use DropDownButtonDifficultySettingsWidget you will get selected value on callback

DropDownButtonDifficultySettingsWidget(
  callback: (selectedValue) {
    print(selectedValue);
/// do the thing you like to have 
  },
),