var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

self.window = UIWindow()

let listViewController:ListViewController = ListViewController()

let navigationController:UINavigationController = UINavigationController(rootViewController: listViewController);

self.window!.rootViewController = navigationController;

self.window!.backgroundColor = UIColor.white

self.window!.makeKeyAndVisible()

return true

}