Radio

main.dart

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int _radioValue1 = -1;

  void _handleRadioValueChange1(int value) {
    setState(() {
      _radioValue1 = value;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          title: Text('Radio'),
        ),
        body: Container(
          child: new Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              new Radio(
                value: 0,
                groupValue: _radioValue1,
                onChanged: _handleRadioValueChange1,
              ),
              new Text(
                'Valor 1',
                style: new TextStyle(fontSize: 16.0),
              ),
              new Radio(
                value: 1,
                groupValue: _radioValue1,
                onChanged: _handleRadioValueChange1,
              ),
              new Text(
                'Valor 2',
                style: new TextStyle(
                  fontSize: 16.0,
                ),
              ),
              new Radio(
                value: 2,
                groupValue: _radioValue1,
                onChanged: _handleRadioValueChange1,
              ),
              new Text(
                'Valor 3',
                style: new TextStyle(fontSize: 16.0),
              ),
            ],
          ),
        ),
      ),
    );
  }
}