Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      initialRoute: '/',
      routes: <String, WidgetBuilder> { //5 
        '/': (context) => MyHomePage(title: 'Home Page'),
        '/first': (BuildContext context) => new FirstPage(), //6
        '/second' : (BuildContext context) => new SecondPage() //7
      },
    );
  }