检查UIAlertController TextField以启用该按钮

Question

我有一个带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)


}

我想要做的是在文本字段为空时执行检查以禁用SAVE按钮,就像想要创建NewAlbum的iOS的图片应用程序一样.请有人能解释一下该怎么办？

Answer 1

在没有使用通知中心的情况下,有一种更简单的方法,在swift中:

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

我首先创建alertcontroller,最初禁用保存操作.然后,当添加文本字段时,包含通知以在处理程序和该选择器中观察其更改,只需切换启用保存操作的属性.

这就是我的意思:

//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 - 我直接从苹果示例得到了这个模式.他们有一个非常好的示例项目,概述了UICatalog示例中的一些模式:https: //developer.apple.com/library/content/samplecode/UICatalog/Introduction/Intro.html