检查 UIAlertController TextField 以启用按钮

Posted 2023-02-21

【中文标题】检查 UIAlertController TextField 以启用按钮

【英文标题】：Check on UIAlertController TextField for enabling the button

【发布时间】：2014-08-19 22:01:34

【问题描述】：

我有一个带有文本字段和两个按钮的 AlertController：CANCEL 和 SAVE。这是代码：

@IBAction func addTherapy(sender: AnyObject)

    let addAlertView = UIAlertController(title: "New Prescription", message: "Insert a name for this prescription", preferredStyle: UIAlertControllerStyle.Alert)

    addAlertView.addAction(UIAlertAction(title: "Cancel",
                                         style: UIAlertActionStyle.Default,
                                         handler: nil))

    addAlertView.addAction(UIAlertAction(title: "Save",
                                         style: UIAlertActionStyle.Default,
                                         handler: nil))

    addAlertView.addTextFieldWithConfigurationHandler(textField in textField.placeholder = "Title")


    self.presentViewController(addAlertView, animated: true, completion: nil)

我想要做的是对文本字段进行检查，以在文本字段为空时禁用“保存”按钮，就像您想要创建新专辑时 ios 的图片应用程序一样。请有人可以解释我该怎么做？

【参考方案1】：

有一个更简单的方法，不使用通知中心，快速：

weak var actionToEnable : UIAlertAction?

func showAlert()

    let titleStr = "title"
    let messageStr = "message"

    let alert = UIAlertController(title: titleStr, message: messageStr, preferredStyle: UIAlertControllerStyle.alert)

    let placeholderStr =  "placeholder"

    alert.addTextField(configurationHandler: (textField: UITextField) in
        textField.placeholder = placeholderStr
        textField.addTarget(self, action: #selector(self.textChanged(_:)), for: .editingChanged)
    )

    let cancel = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler:  (_) -> Void in

    )

    let action = UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler:  (_) -> Void in
        let textfield = alert.textFields!.first!

        //Do what you want with the textfield!
    )

    alert.addAction(cancel)
    alert.addAction(action)

    self.actionToEnable = action
    action.isEnabled = false
    self.present(alert, animated: true, completion: nil)


func textChanged(_ sender:UITextField) 
    self.actionToEnable?.isEnabled  = (sender.text! == "Validation")

【讨论】：

在 Swift 3 代码中，缺少actionToEnable 变量定义

太棒了..！很酷的答案

【参考方案2】：

我将首先创建警报控制器，并在最初禁用保存操作。然后在添加文本字段时包含一个通知以观察其在处理程序中的变化，并在该选择器中切换保存操作启用属性。

这就是我要说的：

//hold this reference in your class
weak var AddAlertSaveAction: UIAlertAction?

@IBAction func addTherapy(sender : AnyObject) 

    //set up the alertcontroller
    let title = NSLocalizedString("New Prescription", comment: "")
    let message = NSLocalizedString("Insert a name for this prescription.", comment: "")
    let cancelButtonTitle = NSLocalizedString("Cancel", comment: "")
    let otherButtonTitle = NSLocalizedString("Save", comment: "")

    let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)

    // Add the text field with handler
    alertController.addTextFieldWithConfigurationHandler  textField in
        //listen for changes
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "handleTextFieldTextDidChangeNotification:", name: UITextFieldTextDidChangeNotification, object: textField)
    


    func removeTextFieldObserver() 
        NSNotificationCenter.defaultCenter().removeObserver(self, name: UITextFieldTextDidChangeNotification, object: alertController.textFields[0])
    

    // Create the actions.
    let cancelAction = UIAlertAction(title: cancelButtonTitle, style: .Cancel)  action in
        NSLog("Cancel Button Pressed")
        removeTextFieldObserver()
    

    let otherAction = UIAlertAction(title: otherButtonTitle, style: .Default)  action in
        NSLog("Save Button Pressed")
        removeTextFieldObserver()
    

    // disable the 'save' button (otherAction) initially
    otherAction.enabled = false

    // save the other action to toggle the enabled/disabled state when the text changed.
    AddAlertSaveAction = otherAction

    // Add the actions.
    alertController.addAction(cancelAction)
    alertController.addAction(otherAction)

    presentViewController(alertController, animated: true, completion: nil)
 

    //handler
func handleTextFieldTextDidChangeNotification(notification: NSNotification) 
    let textField = notification.object as UITextField

    // Enforce a minimum length of >= 1 for secure text alerts.
    AddAlertSaveAction!.enabled = textField.text.utf16count >= 1

我在另一个项目中这样做 - 我直接从苹果示例中获得了这种模式。他们有一个很好的示例项目，在 UICatalog 示例中概述了其中一些模式：https://developer.apple.com/library/content/samplecode/UICatalog/Introduction/Intro.html

【讨论】：

你帮了我很多忙！非常感谢！

使用通知过于笨拙（而且不可靠，而且工作量太大）。这就是为什么有文本字段委托和操作的原因。在这里查看我的答案：***.com/a/25628065/341994

马特的回答更好

它给出错误：由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'-[Naina.SearchVillageTableViewController handleTextFieldTextDidChangeNotification:]：无法识别的选择器发送到实例 0x7f802dc41f50'

【参考方案3】：

@spoek 给出的 Swift 3.0 更新解决方案

func showAlert()
    
        let titleStr = "title"
        let messageStr = "message"

        let alert = UIAlertController(title: titleStr, message: messageStr, preferredStyle: UIAlertControllerStyle.alert)

        let placeholderStr =  "placeholder"

        alert.addTextField(configurationHandler: (textField: UITextField) in
            textField.placeholder = placeholderStr
            textField.addTarget(self, action: #selector(self.textChanged(_:)), for: .editingChanged)
        )

        let cancel = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler:  (_) -> Void in

        )

        let action = UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler:  (_) -> Void in
            let textfield = alert.textFields!.first!

            //Do what you want with the textfield!
        )

        alert.addAction(cancel)
        alert.addAction(action)

        self.actionToEnable = action
        action.isEnabled = false
        self.present(alert, animated: true, completion: nil)
    

    func textChanged(_ sender:UITextField) 
        self.actionToEnable?.isEnabled  = (sender.text! == "Validation")
    

【讨论】：

真的很有帮助。谢谢:)

【参考方案4】：

我实现了 UIAlertController 的子类，用于方便地添加文本字段以及相关的按钮启用和禁用。基本逻辑与 Sourabh Sharma 类似，但一切都封装在这个子类中以保持整洁。如果您的项目涉及大量此类警报功能，这应该会有所帮助。

public class TextEnabledAlertController: UIAlertController 
  private var textFieldActions = [UITextField: ((UITextField)->Void)]()

  func addTextField(configurationHandler: ((UITextField) -> Void)? = nil, textChangeAction:((UITextField)->Void)?) 
      super.addTextField(configurationHandler:  (textField) in
        configurationHandler?(textField)

        if let textChangeAction = textChangeAction 
            self.textFieldActions[textField] = textChangeAction
            textField.addTarget(self, action: #selector(self.textFieldChanged), for: .editingChanged)

        
    )



  @objc private func textFieldChanged(sender: UITextField) 
    if let textChangeAction = textFieldActions[sender] 
        textChangeAction(sender)
    
  

要使用它，只需在添加文本字段时提供一个 textChangeAction 块：

    alert.addTextField(configurationHandler:  (textField) in
        textField.placeholder = "Your name"
        textField.autocapitalizationType = .words
    )  (textField) in
        saveAction.isEnabled = (textField.text?.characters.count ?? 0) > 0
    

有关完整示例，请参阅the git page。