检查 UIAlertController TextField 以启用按钮

Question

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？

Answer 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")
}

Answer 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

Answer 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")
    }

Answer 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。