Question

我有一个警报视图，我想在照片视图中显示。

照片显示在列表中，可以推送到全屏视图。

正在以编程方式显示照片视图。我认为这是导致问题的原因，因为警报视图试图在已经呈现的（照片）视图之上呈现另一个视图。

警报视图正在尝试显示，但收到此错误：

Warning: Attempt to present <UIAlertController: 0x147d2c6b0>  on <LiveDeadApp.ListViewController: 0x147d614c0> which is already presenting (null)

可能有问题的一行就是这一行：

 self.present(textPrompt, animated: true, completion: nil)

这是主要的列表视图

这是截屏时的主要列表视图

这是主要的照片视图

这是主照片视图中的popover（通过＆＃34; i＆＃34;按钮访问）

在主照片视图上拍摄屏幕截图时，不会发生警报视图。但是，当设备的方向发生变化时，照片视图会返回列表并显示警告。

这就是我要做的事情：

iOS 10中的Swift 3

谢谢！

以下是列表视图和照片视图的代码：

import UIKit
import Kingfisher
import SKPhotoBrowser

class ListViewCell: UITableViewCell {

@IBOutlet weak var Cellimage: UIImageView!

@IBOutlet weak var cellVenue: UILabel!

@IBOutlet weak var cellLocation: UILabel!

@IBOutlet weak var cellDate: UILabel!
@IBOutlet weak var aiView: UIActivityIndicatorView!
}

class ListViewController: UITableViewController {

var subcategory:Subcategory!

var objects:[[String:String]] = [[String:String]]()

var images = [SKPhotoProtocol]()



override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)


}

override func viewDidLoad() {
    super.viewDidLoad()


    self.tableView.separatorStyle = .none

    self.view.backgroundColor = UIColor.black

    self.navigationController?.navigationBar.titleTextAttributes = [NSForegroundColorAttributeName: UIColor.white]

    navigationController!.navigationBar.barTintColor = UIColor.black

    let requireTextInput = "require text input"
    // add observer for screen shot
    NotificationCenter.default.addObserver(forName: NSNotification.Name.UIApplicationUserDidTakeScreenshot, object: nil, queue: OperationQueue.main, using:
        { notification in

            self.definesPresentationContext = true

            var inputTextField = UITextField()

            let textPrompt = UIAlertController(title: "Test!", message: "Testing!", preferredStyle: .alert)

            textPrompt.addAction(UIAlertAction(title: "Continue", style: .default, handler: {
                (action) -> Void in
                // if the input match the required text

                let str = inputTextField.text
                if str == requireTextInput {
                    print("right")
                } else {
                    print("wrong")
                }

            }))

            textPrompt.addTextField(configurationHandler: {(textField: UITextField!) in
                textField.placeholder = ""
                inputTextField = textField

            })

            self.present(textPrompt, animated: true, completion: nil)

    })

    if subcategory != nil {
        self.title = subcategory.title
        self.objects = subcategory.photos

        createLocalPhotos()

        self.tableView.reloadData()
    }


}

func createLocalPhotos() {

    for item in objects {
        let photo = SKPhoto.photoWithImageURL(item["url"]!)
        photo.shouldCachePhotoURLImage = true
        images.append(photo)
    }

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

override func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return objects.count
}

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell: ListViewCell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! ListViewCell

    let item = objects[indexPath.row]

    let title = item["title"]
    let location = item["location"]
    let date = item["date"]
    let urlSrt = item["url"]


    cell.cellVenue.text = title
    cell.cellLocation.text = location
    cell.cellDate.text = date

    if let url = URL(string: urlSrt!) {
        cell.aiView.startAnimating()
        cell.Cellimage.kf.setImage(with: url, placeholder: nil, options: nil, progressBlock: nil, completionHandler: { (image, error, cacheType, url) in
            cell.aiView.stopAnimating()
        })
    }

    return cell

}

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let cell = tableView.cellForRow(at: indexPath) as! ListViewCell

    if(cell.Cellimage.image != nil ) {
        SKPhotoBrowserOptions.displayToolbar = false
        SKPhotoBrowserOptions.displayCounterLabel = false
        SKPhotoBrowserOptions.displayBackAndForwardButton = false
        SKPhotoBrowserOptions.displayAction = false
        SKPhotoBrowserOptions.displayDeleteButton = true
        SKPhotoBrowserOptions.displayHorizontalScrollIndicator = false
        SKPhotoBrowserOptions.displayVerticalScrollIndicator = false
        SKPhotoBrowserOptions.displayStatusbar = false
        SKPhotoBrowserOptions.disableVerticalSwipe = true
        SKPhotoBrowserOptions.bounceAnimation = false
        let browser = ExtendedSKPhotoBrowser(originImage: cell.Cellimage.image!, photos: images, animatedFromView: cell)

        let btnSize = 80//24 * UIScreen.main.scale

        browser.updateCloseButton(UIImage(named: "ic_close_white")!, size: CGSize(width: btnSize, height: btnSize))
        browser.updateDeleteButton(UIImage(named: "ic_info_white")!, size: CGSize(width: btnSize, height: btnSize))
        browser.initializePageIndex(indexPath.row)
        browser.delegate = self
        present(browser, animated: true, completion: {})
        browser.toggleControls()
    }
}

override var prefersStatusBarHidden: Bool {
    get {
        return true
    }
}


var popOverVC:PopUpViewController!
}

extension ListViewController: SKPhotoBrowserDelegate {
func didShowPhotoAtIndex(_ index: Int) {






}

func willDismissAtPageIndex(_ index: Int) {

}

private func willShowActionSheet(photoIndex: Int) {
    // do some handle if you need
}

func didDismissAtPageIndex(_ index: Int) {
}

func didDismissActionSheetWithButtonIndex(_ buttonIndex: Int, photoIndex: Int) {
    // handle dismissing custom actions
}

func removePhoto(_ browser: SKPhotoBrowser, index: Int, reload: (() -> Void)) {
    popOverVC = self.storyboard?.instantiateViewController(withIdentifier: "sbPopUpID") as! PopUpViewController
    popOverVC.photoData = objects[index]

}

func viewForPhoto(_ browser: SKPhotoBrowser, index: Int) -> UIView? {
    return tableView.cellForRow(at: IndexPath(row: index, section: 0))
}
}


open class ExtendedSKPhotoBrowser: SKPhotoBrowser {

open override var preferredStatusBarStyle: UIStatusBarStyle {
    return .lightContent // white statusbar, .default is black
}

open override var prefersStatusBarHidden: Bool {
    return true
}
}

Answer 1

问题非常简单，您尝试在当前显示的UIAlertController上显示另一个UIAlertController。

那么，如何解决这种情况？

您需要获取当前视图控制器中使用的所有UIAlertController的列表。
您必须检查当前视图控制器（或其他视图控制器，如果您正在执行异步请求）中显示警报的逻辑。
当您想在另一个上方显示一个提醒时，您的代码必须如此。

假设 loadingAlert 当前显示在屏幕上：

self.loadingAlert.dismiss(animated: true, completion: {
     let anotherAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
     let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
     anotherAlert.addAction(okAction)
     self.present(anotherAlert, animated: true, completion: nil)
})

你必须在下一个出现之前解雇第一个。我做了这个答案，解除了没有按钮的警报，以提高效率。

那么，带有操作按钮的提醒呢？

单击其中一个操作后，它将自动关闭   您创建的UIAlertController上的按钮。

但是，如果您同时显示两个包含UIAlertController的{{1}}，则问题仍然存在。您需要重新检查每个逻辑，或者您可以在每个操作的处理程序中处理它：

UIButton

答案迈克：

self.connectionErrorAlert.dismiss(animated: true, completion: {
     let anotherAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
     let okAction = UIAlertAction(title: "OK", style: .default, handler: {action in
            let nextAlert = UIAlertController(title: "New One", message: "The Previous one is dismissed", preferredStyle: .alert)
            self.present(nextAlert, animated: true, completion: nil)
     })
     anotherAlert.addAction(okAction)
     self.present(anotherAlert, animated: true, completion: nil)
})

感谢@Luke答案：https://stackoverflow.com/a/30741496/3378606

Answer 2

嘿，我尝试了一个似乎更有效的简单解决方案，并且能够在第一个警报之前显示第二个警报，该警报将一直存在（无需在用户回答问题之前将其关闭）：

if self.presentedViewController==nil{
    self.present(MyAlert, animated: true, completion: nil)
}else{
    self.presentedViewController!.present(MyAlert, animated: true, completion: nil)
}

Answer 3

在ViewDidLoad中，
设weak变量，例如weak var weakSelf = self

在NotificationCenter，
目前textPropmt喜欢

weak var weakSelf = self
NotificationCenter.default.addObserver(forName: NSNotification.Name.UIApplicationUserDidTakeScreenshot, object: nil, queue: OperationQueue.main, using:
        { notification in
 DispatchQueue.main.async(execute: {
  //create textPrompt here in Main Thread
  weakSelf.present(textPrompt, animated: true, completion: nil)
 })
})

Answer 4

Duplicated from my answer here

在我的情况下，我无法将我的类置于类中。所以，这就是我得到的：

let viewController = self // I had viewController passed in as a function,
                          // but otherwise you can do this


// Present the view controller
let currentViewController = UIApplication.shared.keyWindow?.rootViewController
currentViewController?.dismiss(animated: true, completion: nil)

if viewController.presentedViewController == nil {
    currentViewController?.present(alert, animated: true, completion: nil)
} else {
    viewController.present(alert, animated: true, completion: nil)
}

Answer 5

我遇到了这个问题，并一直追踪到这个问题。这是一个带有两个按钮的简单应用程序。轻按第一个按钮会导致“ 2019-03-05 16：58：04.094541-0500 ReadJason [41100：1610082]警告：尝试呈现已经呈现的错误”。

此问题是由于将按钮2复制到按钮1引起的。每个按钮都与一个动作（btn1和btn2）相关联。当我将btn2复制为btn1时，与btn2的联系已包含在btn1的代码中。然后，我将绑定添加到btn1，这导致两个发送事件与btn1绑定-这就是导致错误的原因。

检查按钮1的事件将显示两个操作：screen shot showing the two actions。删除不需要的操作可以清除错误。

screen shot of main.storyboard

<pre><code>    
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIButton *btn1;
@property (weak, nonatomic) IBOutlet UIButton *btn2;
@end

@implementation ViewController

- (void)viewDidLoad {
   [super viewDidLoad];
}

- (IBAction)btn1:(id)sender {
   UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Btn1"
                   message:@"This is Btn1." preferredStyle:UIAlertControllerStyleAlert];

   UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {}];

   [alert addAction:defaultAction];
   [self presentViewController:alert animated:YES completion:nil];
}

- (IBAction)btn2:(id)sender {
   UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Btn2"
                     message:@"This is Btn2." preferredStyle:UIAlertControllerStyleAlert];

   UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {}];

   [alert addAction:defaultAction];
   [self presentViewController:alert animated:YES completion:nil];
}
</code></pre>

Answer 6

我相信，您需要确定是否已经有另一个AlerViewController试图在ViewController上表示自己。

至少那是我的问题。

尝试在已经呈现的View Controller上呈现UIAlertController（null）[Swift]

6 个答案: