main.dart

void main() {
  runApp(MyApp());

}
final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
     navigatorObservers: [MyRouteObserver()],
      routes: {
       'pageone': (context) => PageOne(),
       'pagetwo': (context) => PageTwo()

      },
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}