Question

我有一个应用程序，可以显示UICollectionView中的文档。每个UICollectionViewCell都有一个按钮（与didSelectItemAt所执行的按钮不同）。此按钮将弹出一个自定义弹出窗口，该弹出窗口是我使用UIViewController创建的。显示为Over Current Context。此弹出窗口显示了一个选项列表，其中包括Delete document。当用户选择后一个选项时，我希望出现UIAlertController以确认删除。这是我面临的问题。

这是我的代码：

我得到的错误是：

由于未捕获的异常“ NSInvalidArgumentException”而终止应用程序，原因：“应用程序尝试以模态形式显示活动控制器

自定义弹出窗口（UIViewController）

protocol DismissOptionShowDeleteAlert {
    func showDeleteAlert()
}

class MoreOptionsOnPDFViewController: UIViewController, UITableViewDataSource, UITableViewDelegate{

var showDeleteAlertDelegate: DismissOptionShowDeleteAlert!

/ TAP ON ROW
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath){

    ...

     }else if indexPath == [0,4]{ // DELETE DOCUMENT

        DispatchQueue.main.async {
            self.dismiss(animated: true) {
                self.showDeleteAlertDelegate.showDeleteAlert()
            }
        }
    }

    ...

}

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 ...")
    }
}

}

UIAlertController结构：

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)
}

}

Answer 1

这正是您的错误所说的。您似乎正在展示视图控制器vc，而不是alert

的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.
    }

}

Answer 2

您提出的错误。您需要显示的警报不是vc。

在下面替换您的代码。

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)
    }

}

Answer 3

替换行

vc.present(vc, animated: true, completion: nil)

到

vc.present(alert, animated: true, completion: nil)

由于-'''应用程序试图以模态形式显示活动控制器，因此无法显示UIAlertController

3 个答案: