import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

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

  @override
  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
}

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  late TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TextEditingController();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: TextField(
          controller: _controller,
          onSubmitted: (String value) async {
            await showDialog<void>(
              context: context,
              builder: (BuildContext context) {
                return AlertDialog(
                  title: const Text('Thanks!'),
                  content: Text(
                      'You typed "$value", which has length ${value.characters.length}.'),
                  actions: <Widget>[
                    TextButton(
                      onPressed: () {
                        Navigator.pop(context);
                      },
                      child: const Text('OK'),
                    ),
                  ],
                );
              },
            );
          },
        ),
      ),
    );
  }
}