Input form fields in flutter

FormFields.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

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

String choice;
String _radioValue;
String _selectedCity;

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyPage(),
    );
  }
}

class MyPage extends StatefulWidget {
  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State<MyPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.green,
        leading: Icon(Icons.contact_mail),
        title: Text("Personal Details"),
        centerTitle: true,
      ),
      body: SingleChildScrollView(
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 10),
          child: Column(
            children: <Widget>[
              SizedBox(
                height: 50,
              ),
              TextFormField(
                decoration: InputDecoration(
                  errorStyle: TextStyle(color: Colors.red, fontSize: 15.0),
                  labelText: "Enter your Name",
                  hintStyle: TextStyle(
                    color: Colors.grey,
                    fontSize: 16.0,
                  ),
                  prefixIcon: Icon(
                    Icons.person,
                  ),
                ),
              ),
              SizedBox(height: 25),
              TextFormField(
                inputFormatters: [
                  WhitelistingTextInputFormatter.digitsOnly,
                  new LengthLimitingTextInputFormatter(10),
                ],
                keyboardType: TextInputType.number,
                decoration: InputDecoration(
                  errorStyle: TextStyle(color: Colors.red, fontSize: 15.0),
                  labelText: "Enter your Mobile Number",
                  hintStyle: TextStyle(
                    color: Colors.grey,
                    fontSize: 16.0,
                  ),
                  prefixIcon: Icon(
                    Icons.phone,
                  ),
                ),
              ),
              SizedBox(height: 25),
              Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: <Widget>[
                  Text("Are you a programmer?"),
                  SizedBox(width: 25),
                  Radio(
                    value: 'one',
                    groupValue: _radioValue,
                    onChanged: radioButtonChanges,
                  ),
                  Text(
                    "Yes",
                  ),
                  Radio(
                    value: 'two',
                    groupValue: _radioValue,
                    onChanged: radioButtonChanges,
                  ),
                  Text(
                    "No",
                  ),
                ],
              ),
              SizedBox(
                height: 25,
              ),
              TextFormField(
                decoration: InputDecoration(
                  errorStyle: TextStyle(color: Colors.red, fontSize: 15.0),
                  labelText: "Enter your Email ID",
                  hintStyle: TextStyle(
                    color: Colors.grey,
                    fontSize: 16.0,
                  ),
                  prefixIcon: Icon(
                    Icons.mail,
                  ),
                ),
              ),
              SizedBox(
                height: 25,
              ),
              Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
                  Text("Enter your city"),
                  SizedBox(width: 25),
                  new DropdownButton<String>(
                    value: _selectedCity,
                    items: <String>['City-A', 'City-B', 'City-C', 'City-D']
                        .map((String value) {
                      return new DropdownMenuItem<String>(
                        value: value,
                        child: new Text(value),
                      );
                    }).toList(),
                    onChanged: (newValue) {
                      setState(() {
                        _selectedCity = newValue;
                        print(_selectedCity);
                      });
                    },
                  ),
                ],
              ),
              SizedBox(height: 25),
              Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
                  new RaisedButton(
                    textColor: Colors.white,
                    color: Colors.red,
                    onPressed: () {},
                    child: new Text("Reset"),
                  ),
                  new RaisedButton(
                    textColor: Colors.white,
                    color: Colors.green,
                    onPressed: () {},
                    child: new Text("Submit"),
                  ),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }

  void radioButtonChanges(String value) {
    setState(() {
      _radioValue = value;
      switch (value) {
        case 'one':
          choice = "He is a programmer !";
          break;
        case 'two':
          choice = "No, He is not a Programmer !";
          break;
        default:
          choice = null;
      }
      debugPrint(choice);
    });
  }
}