flutter/packages/flutter_tools/templates/create/lib/main.dart.tmpl

import 'package:flutter/material.dart';
{{#withDriverTest?}}
import 'package:flutter_driver/driver_extension.dart';
{{/withDriverTest?}}

void main() {
{{#withDriverTest?}}
  // Starts the app with Flutter Driver extension enabled to allow Flutter Driver
  // to test the app.
  enableFlutterDriverExtension();
{{/withDriverTest?}}
  runApp(
    new MaterialApp(
      title: 'Flutter Demo',
      routes: <String, WidgetBuilder>{
        '/': (BuildContext context) => new FlutterDemo()
      }
    )
  );
}

class FlutterDemo extends StatefulWidget {
  _FlutterDemoState createState() => new _FlutterDemoState();
}

class _FlutterDemoState extends State<FlutterDemo> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Flutter Demo')
      ),
      body: new Center(
        child: new Text('Button tapped $_counter time${ _counter == 1 ? '' : 's' }.')
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(
          icon: Icons.add
        )
      )
    );
  }
}