[Widget]ラジオボタンを使う

import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
  RamenKind yourChoice = RamenKind.miso;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          title: const Text('サンプル'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              RadioButton(
                label: 'みそ',
                groupValue: yourChoice,
                value: RamenKind.miso,
                onChanged: (newValue) => setState(() {
                  yourChoice = newValue;
                }),
              ),
              RadioButton(
                label: 'しお',
                groupValue: yourChoice,
                value: RamenKind.sio,
                onChanged: (newValue) => setState(() {
                  yourChoice = newValue;
                }),
              ),
              RadioButton(
                label: 'しょうゆ',
                groupValue: yourChoice,
                value: RamenKind.shoYu,
                onChanged: (newValue) => setState(() {
                  yourChoice = newValue;
                }),
              ),
              Text('$yourChoiceを選択しています'),
            ],
          ),
        ),
      ),
    );
  }
}
enum RamenKind { miso, sio, shoYu }
class RadioButton extends StatelessWidget {
  const RadioButton({
    Key? key,
    required this.label,
    required this.groupValue,
    required this.value,
    required this.onChanged,
  }) : super(key: key);
  final String label;
  final RamenKind groupValue;
  final RamenKind value;
  final ValueChanged<RamenKind> onChanged;
  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        if (value == groupValue) {
          return;
        }
        onChanged(value);
      },
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Radio<RamenKind>(
            groupValue: groupValue,
            value: value,
            onChanged: (RamenKind? newValue) {
              onChanged(newValue!);
            },
          ),
          Text(label)
        ],
      ),
    );
  }
}

class RadioButton extends StatelessWidget {
  const RadioButton({
    Key? key,
    required this.label,
    required this.groupValue,
    required this.value,
    required this.onChanged,
  }) : super(key: key);
  final String label;
  final RamenKind groupValue;
  final RamenKind value;
  final ValueChanged<RamenKind> onChanged;
  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        if (value == groupValue) {
          return;
        }
        onChanged(value);
      },
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Radio<RamenKind>(
            groupValue: groupValue,
            value: value,
            onChanged: (RamenKind? newValue) {
              onChanged(newValue!);
            },
          ),
          Text(label)
        ],
      ),
    );
  }
}