Flutter App 32: Change the class StatelessWidget to class StatefulWidget

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(new FriendlychatApp());
}

class FriendlychatApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "Friendlychat",
      home: new ChatScreen(),
    );
  }
}

/*
class ChatScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text("Friendlychat")),
    );
  }
}
*/


class ChatScreen extends StatefulWidget {
  @override
  State createState() => new ChatScreenState();
} 

class ChatScreenState extends State<ChatScreen> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text("Friendlychat")),
    );
  }
}