Hello world in flutter

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String displayname='Stranger';

  String inputname='';

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
      appBar: new AppBar(title: new Text(widget.title),
      ),
      body:Container(
        margin: EdgeInsets.all(20.0),
        child: Column(
        children: <Widget>[
          TextField(
            decoration: InputDecoration(
              labelText: 'Enter your name',
            
            ),
            onChanged: (newValue) { 
             inputname=newValue;
             },

          ),
          Divider(),
          RaisedButton(
            child: Icon(Icons.account_circle),
            onPressed: (){setState(() {
                displayname=inputname;          
                        });},
          ),
          Divider(),
          Text("Hello $displayname, how are you?")

        ],
      ),
      )
    );
  }
}