how to form radio button group in flutter code example

Example: FormBuilderRadioGroup sample code for radio button flutter

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
        title: Text("Flutter Radio Button Group Example"),
        ),
        body: SafeArea(
          child : Center(
 
          child:RadioGroup(),
 
          )
        )
      ),
    );
  }
}
 
class RadioGroup extends StatefulWidget {
  @override
  RadioGroupWidget createState() => RadioGroupWidget();
}
 
class FruitsList {
  String name;
  int index;
  FruitsList({this.name, this.index});
}
 
class RadioGroupWidget extends State {
 
  // Default Radio Button Item
  String radioItem = 'Mango';
 
  // Group Value for Radio Button.
  int id = 1;
 
  List fList = [
    FruitsList(
      index: 1,
      name: "Mango",
    ),
    FruitsList(
      index: 2,
      name: "Apple",
    ),
    FruitsList(
      index: 3,
      name: "Banana",
    ),
    FruitsList(
      index: 4,
      name: "Cherry",
    ),
  ];
 
  Widget build(BuildContext context) {
    return Column(
        children: [
           Padding(
            padding : EdgeInsets.all(14.0),
            child: Text('$radioItem', style: TextStyle(fontSize: 23))
              ),
 
           Expanded(
            child: Container(
            height: 350.0,
            child: Column(
              children: 
                fList.map((data) => RadioListTile(
                  title: Text("${data.name}"),
                  groupValue: id,
                  value: data.index,
                  onChanged: (val) {
                    setState(() {
                      radioItem = data.name ;
                      id = data.index;
                    });
                  },
                )).toList(),
            ),
          )),
          
        ],
    );
  }
}