Ios 由于-'；无法显示UIAlertController''；应用程序试图以模态方式呈现活动控制器'；

我有一个在

UICollectionView

中显示文档的应用程序。每个

UICollectionViewCell

都有一个按钮（与

didSelectItemAt

执行的按钮不同）。此按钮将显示一个自定义弹出窗口，我使用

UIViewController

创建了该弹出窗口。它在当前上下文中显示

。此弹出窗口显示选项列表，其中包括
删除文档
。当用户选择后一个选项时，我希望出现一个
UIAlertController
来确认删除。这是我面临的问题

这是我的密码：

我得到的错误是：

由于未捕获异常“NSInvalidArgumentException”而终止应用程序，
原因：“应用程序试图以模态方式呈现活动控制器

自定义弹出窗口（UIViewController）

UICollectionView:

class CollectionViewFolder: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate ,UICollectionViewDelegateFlowLayout, MoreInfoDocument, MoveFolder, ScanObjectMovedFolder, DismissOptionShowDeleteAlert{

// SHOW DELETE CONFIRMATION ALERT
func showDeleteAlert() {

    Alerts.deleteDocumentConfirm(on: self) {
        // DELETE DOCUMENT FROM SERVER
        print("Delete document ...")
    }
}

}

import Foundation
import UIKit

struct Alerts {
private static func showBasicAlert(on vc: UIViewController, with title: String, message: String, action: @escaping (() -> ())){

    let alert =  UIAlertController.init(title: title, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction.init(title: "OK", style: .default) { (UIActionAlert) in

        action()
    }

    let cancelAction = UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil)

    alert.addAction(okAction)
    alert.addAction(cancelAction)
    DispatchQueue.main.async {
        vc.present(vc, animated: true, completion: nil)
    }

}


static func deleteDocumentConfirm(on vc: UIViewController, action: @escaping (() -> ())){
    showBasicAlert(on: vc, with: "Please Confirm Delete", message: "", action: action)
}

}    

UIAlertController结构：

class CollectionViewFolder: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate ,UICollectionViewDelegateFlowLayout, MoreInfoDocument, MoveFolder, ScanObjectMovedFolder, DismissOptionShowDeleteAlert{

// SHOW DELETE CONFIRMATION ALERT
func showDeleteAlert() {

    Alerts.deleteDocumentConfirm(on: self) {
        // DELETE DOCUMENT FROM SERVER
        print("Delete document ...")
    }
}

}

import Foundation
import UIKit

struct Alerts {
private static func showBasicAlert(on vc: UIViewController, with title: String, message: String, action: @escaping (() -> ())){

    let alert =  UIAlertController.init(title: title, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction.init(title: "OK", style: .default) { (UIActionAlert) in

        action()
    }

    let cancelAction = UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil)

    alert.addAction(okAction)
    alert.addAction(cancelAction)
    DispatchQueue.main.async {
        vc.present(vc, animated: true, completion: nil)
    }

}


static func deleteDocumentConfirm(on vc: UIViewController, action: @escaping (() -> ())){
    showBasicAlert(on: vc, with: "Please Confirm Delete", message: "", action: action)
}

}    

这正是你的错误所说的。您似乎正在显示视图控制器
vc
，而不是
vc

private static func showBasicAlert(on vc: UIViewController, with title: String, message: String, action: @escaping (() -> ())){

    let alert =  UIAlertController.init(title: title, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction.init(title: "OK", style: .default) { (UIActionAlert) in

        action()
    }

    let cancelAction = UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil)

    alert.addAction(okAction)
    alert.addAction(cancelAction)
    DispatchQueue.main.async {
        vc.present(alert, animated: true, completion: nil) // You should be presenting the alert here.
    }

}

你错了。您需要显示警报，而不是vc

用您的代码替换下面的内容

struct Alerts {
private static func showBasicAlert(on vc: UIViewController, with title: String, message: String, action: @escaping (() -> ())){

    let alert =  UIAlertController.init(title: title, message: message, preferredStyle: .alert)
    let okAction = UIAlertAction.init(title: "OK", style: .default) { (UIActionAlert) in

        action()
    }

    let cancelAction = UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil)

    alert.addAction(okAction)
    alert.addAction(cancelAction)
    DispatchQueue.main.async {
        vc.present(alert, animated: true, completion: nil)
    }

}

换行

vc.present（vc，动画：true，完成：nil）

到

vc.present（警报，动画：true，完成：nil）
可能重复的