如何使警报中的取消按钮取消操作？

Question

我已经提醒你了，但是当应用程序弹出警告时，无论点击“NO”按钮还是“Yes，I'm sure”按钮，该应用程序都会添加该项目。

我的目标是做出“否”的动作，取消动作，这样输入将不会被添加。你能告诉我如何？

import UIKit 

class SecondViewController: UIViewController, UITextFieldDelegate { 
    @IBOutlet weak var input: UITextField! 

    @IBAction func addItem(_ sender: Any) 
    { 
     createAlert(title: "That's a good grail!", message: "Are you sure you want to add this grail?") 

     if (input.text != "") 
     { 
      list.append(input.text!) 
      input.text = "" 
     } 
    } 

    override func viewDidLoad() 
    { 
     super.viewDidLoad() 

     self.input.delegate = self 
    } 

    //HIDE KEYBOARD: 
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
     self.view.endEditing(true) 
    } 

    //PRESSES RETURN KEY: 
    func textFieldShouldReturn(_ textField: UITextField) -> Bool { 
     input.resignFirstResponder() 
     return true 
    } 

    func createAlert (title:String, message:String) 
    { 
     let alertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert) 

     //CREATING OK BUTTON 

     let OKAction = UIAlertAction(title: "Yes, I'm sure!", style: .default) { (action:UIAlertAction!) in 

      // Code in this block will trigger when OK button tapped. 
      print("Ok button tapped"); 

     } 
     alertController.addAction(OKAction) 

     // Create Cancel button 
     let cancelAction = UIAlertAction(title: "No!", style: .cancel) { (action:UIAlertAction!) in 
      print("Cancel button tapped"); 
     } 
     alertController.addAction(cancelAction) 

     // Present Dialog message 
     self.present(alertController, animated: true, completion:nil) 
    } 
} 

编辑：

代码看起来现在这个样子，感谢：

进口的UIKit

类SecondViewController：UIViewController中，UITextFieldDelegate {

@IBOutlet weak var input: UITextField! 

@IBAction func addItem(_ sender: Any) 
{ 
    createAlert(title: "That's a good grail!", message: "Are you sure you want to add this grail?") 

} 



override func viewDidLoad() 
{ 
    super.viewDidLoad() 

    self.input.delegate = self 
} 



override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Dispose of any resources that can be recreated. 
} 


//HIDE KEYBOARD: 
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
    self.view.endEditing(true) 
} 

//PRESSES RETURN KEY: 
func textFieldShouldReturn(_ textField: UITextField) -> Bool { 
    input.resignFirstResponder() 
    return true 
} 


func createAlert (title:String, message:String) 
{ 
    let alertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert) 

    //CREATING OK BUTTON 

    let OKAction = UIAlertAction(title: "Yes, I'm sure!", style: .default) { (action:UIAlertAction!) in 

     // Code in this block will trigger when OK button tapped. 
     print("Ok button tapped"); 
     if (self.self.input.text != "") 
     { 
      list.append(self.input.text!) 
      self.input.text = "" 
     } 

    } 
    alertController.addAction(OKAction) 

    // Create Cancel button 
    let cancelAction = UIAlertAction(title: "No!", style: .cancel) { (action:UIAlertAction!) in 
     print("Cancel button tapped"); 
    } 
    alertController.addAction(cancelAction) 

    // Present Dialog message 
    self.present(alertController, animated: true, completion:nil) 
} 

}

Answer 1

只是简单地把代码添加项目到OK关闭：

class SecondViewController: UIViewController, UITextFieldDelegate { 

@IBOutlet weak var input: UITextField! 

@IBAction func addItem(_ sender: Any) 
{ 
    createAlert(title: "That's a good grail!", message: "Are you sure you want to add this grail?") 
} 

override func viewDidLoad() 
{ 
    super.viewDidLoad() 

    self.input.delegate = self 
} 



override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Dispose of any resources that can be recreated. 
} 


//HIDE KEYBOARD: 
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
    self.view.endEditing(true) 
} 

//PRESSES RETURN KEY: 
func textFieldShouldReturn(_ textField: UITextField) -> Bool { 
    input.resignFirstResponder() 
    return true 
} 


func createAlert (title:String, message:String) 
{ 
    let alertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert) 

    //CREATING OK BUTTON 

    let OKAction = UIAlertAction(title: "Yes, I'm sure!", style: .default) { (action:UIAlertAction!) in 

     // Code in this block will trigger when OK button tapped. 
    if (input.text != "") 
    { 
     list.append(input.text!) 
     input.text = "" 
    } 
     print("Ok button tapped"); 

    } 
    alertController.addAction(OKAction) 

    // Create Cancel button 
    let cancelAction = UIAlertAction(title: "No!", style: .cancel) { (action:UIAlertAction!) in 
     print("Cancel button tapped"); 
    } 
    alertController.addAction(cancelAction) 

    // Present Dialog message 
    self.present(alertController, animated: true, completion:nil) 
} 
} 

Answer 2

您要添加的input.text反正你addItem(_ :)方法显示您UIAlertController后。

所以，如果你想避免input.text总是只有添加时确定按钮被窃听你应该包括在封闭的行动，当你创造了它和的UIAlertController

let OKAction = UIAlertAction(title: "Yes, I'm sure!", style: .default) { [weak self] _ in 

     guard let selfStrong = self else { 
      return 
     } 

     // Code in this block will trigger when OK button tapped. 
     if (selfStrong.input.text != "") { 
      selfStrong.list.append(input.text!) 
      selfStrong.input.text = "" 
     } 
} 

提出后删除

对于取消按钮，您不需要任何操作关闭，除非您还想在点按取消按钮时执行某些操作。

我希望这可以帮助你。

Answer 3

您不是在点击“是，我确定”按钮上追加该项目。删除中的以下代码@IBAction func addItem（_ sender：Any）方法并将其放入OKAction处理程序块。

if (input.text != "") 
    { 
     list.append(input.text!) 
     input.text = "" 
    } 

这样做：

@IBAction func addItem(_ sender: Any) 
    { 
     createAlert(title: "That's a good grail!", message: "Are you sure you want to add this grail?") 


} 

内部方法：FUNC createAlert（标题：字符串消息：字符串）（把这里附加代码）

let OKAction = UIAlertAction(title: "Yes, I'm sure!", style: .default) { (action:UIAlertAction!) in 
     // Code in this block will trigger when OK button tapped. 
     print("Ok button tapped"); 
    if (input.text != "") 
    { 
     list.append(input.text!) 
     input.text = "" 
    } 
}