Basic Flutter Hello World example

main.dart

import 'package:flutter/material.dart';

void main() => runApp(
    MaterialApp(title: 'Test App', home: SafeArea(child: ScaffoldDemo())));

class ScaffoldDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Material(
        child: Column(children: <Widget>[
      AppBarDemo(
          title: Text('Scaffold Demo',
              style: Theme.of(context).textTheme.headline6)),
      Expanded(child: Center(child: Text('Hello world!')))
    ]));
  }
}

class AppBarDemo extends StatelessWidget {
  AppBarDemo({required this.title});

  final Widget title;

  @override
  Widget build(BuildContext context) {
    return Container(
        height: 56.0,
        padding: const EdgeInsets.symmetric(horizontal: 8.0),
        decoration: BoxDecoration(color: Colors.blue[500]),
        child: Row(
          children: <Widget>[
            IconButton(
                icon: Icon(Icons.menu), tooltip: 'Nav Icon', onPressed: null),
            Expanded(child: title),
            IconButton(
                icon: Icon(Icons.search), tooltip: 'Search', onPressed: null)
          ],
        ));
  }
}