Вы можете сделать это в своем классе AppDelegate
func applicationDidBecomeActive(_ application: UIApplication) {
window?.layer.cornerRadius = 10
window?.clipsToBounds = true
window?.backgroundColor = .white
}
А если вы используете класс SceneDelegate, тогда
func sceneDidBecomeActive(_ scene: UIScene) {
window?.layer.cornerRadius = 110
window?.clipsToBounds = true
window?.backgroundColor = UIColor.black
// Called when the scene has moved from an inactive state to an active state.
// Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
}