We will now create a new app that we'll use throughout this chapter to build a fully functioning measure converter:

1. From your favorite editor, create a new app. Name the new app Unit Converter.
2. In the main.dart file, remove the example code and write the code given as follows:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
@override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Measures Converter',
      home: Scaffold(
      appBar: AppBar(
          title: Text('Measures Converter'),
      ),
      body: Center(
          child: Text('Measures Converter'),
      ),),
  );}
}

As you may have noticed, the preceding code makes use of a Stateless widget:

class MyApp extends StatelessWidget {

In the build() method, you describe the widget returned by the method: 

@override
Widget build(BuildContext context) {

The build() method that takes a context and returns a widget:

return MaterialApp(…)

So to summarize, in order to have a stateless widget you need to do the following:

1. Create a class that extends StatelessWidget.
2. Override the build() method.
3. Return a widget.

Once built, a Stateless widget never changes.