警报框未显示。 X 代码是跳过 Swift 中的警报框代码

Posted 2023-02-23

【中文标题】警报框未显示。 X 代码是跳过 Swift 中的警报框代码

【英文标题】：Alert Box Is not showing. X Code is Skip the alert box code in Swift

【发布时间】：2021-08-13 04:43:18

【问题描述】：

当我在ViewController2 中performSegue 然后在ViewController1 中自动调用unwindToMyHours。 那么我不知道为什么 X Code 会跳过呈现Alert BOX 的代码。

OUTPUT -> 其他部分完成。

和 xCode 跳过 -> Task 1 和 task 2

~ViewController2的代码

@IBAction func CancelButtonTapped(_ sender: UIButton) 
    let alert = UIAlertController(title: "Delete Time", message: "Are you sure?", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "Delete", style: .destructive, handler:  [self] _ in
            
            self.deleted = true
            self.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
        ))
        alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
        self.present(alert, animated: true, completion: nil)
 

~ViewController1的代码

@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) 
    if (seg.source as? ViewController2)?.submitted == true 
        loadData()
     else if (seg.source as? ViewController2)?.deleted == true 
        let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler:  alert in
            print("Task 1")
        ))
        present(alert, animated: true) 
            print("Task 2")
        
        print("Else part complete")
    

【参考方案1】：

嗯。 也许您忘记销毁您的第一个警报控制器。

在不破坏第一个警报控制器的情况下，您呈现第二个警报控制器，因此 XCode 无法呈现您的第二个警报控制器。

你的代码看起来不错……让我编辑一下。

~ViewController2的代码

@IBAction func CancelButtonTapped(_ sender: UIButton) 
    let alert = UIAlertController(title: "Delete Time", message: "Are you sure?", preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Delete", style: .destructive, handler:  [self] _ in
        
        self.deleted = true
        self.dismiss(animated: false, completion: nil) // You are forgetting  this
        self.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
    ))
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
    self.present(alert, animated: true, completion: nil)

---

~ViewController1 的代码 -> 相同的代码

@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) 
if (seg.source as? ViewController2)?.submitted == true 
    loadData()
 else if (seg.source as? ViewController2)?.deleted == true 
    let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "OK", style: .default, handler:  alert in
        print("Task 1")
    ))
    present(alert, animated: true) 
        print("Task 2")
    
    print("Else part complete")

【参考方案2】：

这很可能是因为您之前的视图控制器还没有被解雇，并且您不能present 一个新的视图控制器（警报是），直到您的视图控制器成为顶部。等到发生这种情况：

var shouldDisplayDeletedAlert = false

override func viewDidAppear(_ animated: Bool) 
    super.viewDidAppear(animated)
    if shouldDisplayDeletedAlert 
        let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler:  alert in
            print("Task 1")
        ))
        present(alert, animated: true) 
            print("Task 2")
        
        shouldDisplayDeletedAlert = false
    


@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) 
    if (seg.source as? ViewController2)?.submitted == true 
        loadData()
     else if (seg.source as? ViewController2)?.deleted == true 
        shouldDisplayDeletedAlert = true
    

【讨论】：

@iosSwiftLearner is viewDidAppear 在unwindToMyHours 之后被调用？

是的，但是 xcode 再次跳过警报视图显示的代码

@iOSSwiftLearner 很难说没有更多信息。警报代码看起来不错，对我有用