尝试使用 localnotification 呈现其视图不在窗口层次结构中的 UIAlertController [重复]

我试图在用户单击本地通知后呈现 AlertView。 AlertView 有取消或确定选项。

extension ViewController:UNUserNotificationCenterDelegate{


    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {

        print("Tapped in notification")
        if(defaults.object(forKey: "alertOn") != nil){


            // Create the alert controller
            let alertController = UIAlertController(title: "Some text", message: "Some text again", preferredStyle: .alert)


            // Create the actions
            let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default) {
                UIAlertAction in

            }

            let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel) {
                UIAlertAction in
            }

            // Add the actions
            alertController.addAction(okAction)
            alertController.addAction(cancelAction)

            // Present the controller
                self.present(alertController, animated: true, completion: nil)

        }
    }


func triggerNotification(){

        print("notification will be triggered in five seconds..Hold on tight")
        let content = UNMutableNotificationContent()
        content.title = "SomeText"
        content.body = "Some more text"
        content.sound = UNNotificationSound.default()

        let trigger = UNTimeIntervalNotificationTrigger.init(timeInterval: 5.0, repeats: false)
        let request = UNNotificationRequest(identifier:requestIdentifier, content: content, trigger: trigger)

        UNUserNotificationCenter.current().delegate = self as! UNUserNotificationCenterDelegate
        UNUserNotificationCenter.current().add(request){(error) in

            if (error != nil){

                print(error?.localizedDescription)
            }
        }
    }

它应该向我显示警报视图，其中包含确定或取消请求的选项。相反，它向我显示消息UIAlertController 其视图不在窗口层次结构中

当我将警报视图放入 viewdidappear 时，它工作正常，但是当我将其放入 userNotificationCenter 时，我的 AlertView 不会附加到主视图。

代码简述

extension ViewController:UNUserNotificationCenterDelegate{
          func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {

         Present UIAlertView

        }
}

ViewController{

Call to notification when app is in background 
triggerNotification()

triggerNotification(){
 Definition 
}
}

try this

func currentTopViewController() -> UIViewController {
    var topVC: UIViewController? = UIApplication.shared.delegate?.window?.rootViewController
    while topVC?.presentedViewController {
        topVC = topVC?.presentedViewController
    }
    return topVC!
}

并将 VC 表示为

let currentTopVC: UIViewController? = self.currentTopViewController()

currentTopVC.present(alertController, animated: true, completion: nil)