Question

我有action，点击按钮时会创建alert。

此alert包含两个textfields和两个actions（add和dismiss）。

如果add为空，我是否有任何简单的方法可以停用textfields按钮（我稍后会检查第二个是否真的是一个网址但是让我们来看看把事情集中在action这里？

这是我的代码以及我到目前为止所尝试的内容：

@IBAction func addSourceTapped(_ sender: Any) {

    let alert = UIAlertController(title: "Add a News Source", message: nil, preferredStyle: .alert)

    alert.addTextField { (textField) in
        textField.placeholder = "Name"
    }
    alert.addTextField { (textField) in
        textField.placeholder = "Link"
    }

    let name = alert.textFields!.first!.text!
    let link = alert.textFields!.last!.text!

    if name != "" && link != "" {
        alert.actions[0].isEnabled = true
    }

    let action = UIAlertAction(title: "Add", style: .default) { (_) in
        let name = alert.textFields!.first!.text!
        let link = alert.textFields!.last!.text!

        if name != "" && link != "" {

            alert.actions[0].isEnabled = true //doesn't do anything yet..

            if CoreDataHandler.saveSource(name: "\(name)", link: "\(link)") {
                for _ in CoreDataHandler.fetchSource()! {
                }
            }
        }


        self.tableView.reloadData()
    }

    let action2 = UIAlertAction(title: "Dismiss", style: .default)

    alert.addAction(action)
    alert.actions[0].isEnabled = false
    alert.addAction(action2)
    present(alert, animated: true, completion: nil)

}

Answer 1

您无法在任何地方编写UITextField验证代码（启用/禁用操作的代码）!!每次UItextfield更新时都必须执行此验证。因此，为此，您需要从UITextField获取代理以获取其更新

您需要全局保存文本字段并将文本字段的委托分配给ViewController。通过这样做，您可以编写代码来验证UIViewController中的文本字段代码，并以编程方式启用或禁用您的操作

class YOUR_CLASS_NAME:UIViewController,UITextFieldDelegate {

    var alert: UIAlertController!
    var action: UIAlertAction!
    var action2: UIAlertAction!
    var nameTextFeld:UITextField!
    var linkTextFeld:UITextField!

    @IBAction func addSourceTapped(_ sender: Any) {
        alert = UIAlertController(title: "Add a News Source", message: nil, preferredStyle: .alert)
        alert.addTextField { (textField) in
            self.nameTextFeld = textField
            self.nameTextFeld.placeholder = "Name"
            self.nameTextFeld.delegate = self
        }
        alert.addTextField { (textField) in
            self.linkTextFeld = textField
            self.linkTextFeld.placeholder = "Link"
            self.linkTextFeld.delegate = self
        }

        action = UIAlertAction(title: "Add", style: .default) { (_) in
            let name = self.alert.textFields!.first!.text!
            let link = self.alert.textFields!.last!.text!
            if CoreDataHandler.saveSource(name: "\(name)", link: "\(link)") {
              for _ in CoreDataHandler.fetchSource()! {

              }
            }
            self.tableView.reloadData()
        }
        action.isEnabled = false
        action2 = UIAlertAction(title: "Dismiss", style: .default)
        alert.addAction(action)
        alert.actions[0].isEnabled = false
        alert.addAction(action2)
        present(alert, animated: true, completion: nil)
    }

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if !((nameTextFeld.text?.isEmpty)! && (linkTextFeld.text?.isEmpty)!) {
            action.isEnabled = true
        }
        return true
    }
}

Answer 2

通过在添加文本字段时配置

来执行此操作

alert.addTextField(configurationHandler: { (textField) -> Void in
    textField.placeholder = "Name"
    // Other configuration such as textField.autocapitalizationType = .words

    NotificationCenter.default.addObserver(forName: NSNotification.Name.UITextFieldTextDidChange, object: textField, queue: OperationQueue.main) { (notification) in
        let nameField = alert.textFields![0] as UITextField
        let linkField = alert.textFields![1] as UITextField

        action.isEnabled = self.getTextFieldContent(nameField) != "" && self.getTextFieldContent(linkField) != ""
    }
})

您需要为两个文本字段单独执行此操作（尽管您可以通过重用相同的代码来执行此操作）。另请注意，如果您直接在动作的处理程序块中引用文本字段，它将创建一个强引用循环，并且您的控制器将不会被取消。为了避免这种情况，请使用本地可为空的变量（例如

）引用文本字段

var tf: UITextField?

let action = UIAlertAction(title: "Add", style: .default) { (_) in
    guard let textField = tf else {
        return;
    }
    let name = textField.text!
    // Rest the action here
}

alertController.addTextField { (textField) in
    // Configure textField here
    tf = textField
}

Answer 3

你应该更好地使用行动，它比其他答案更简单。如果你尝试使用委托，方法didBeginEditing＆amp; didEndEditing将无法正确处理它。 shouldChangeCharacters也不在范围内，它在文本字段输入之前执行，因此在那里检查textField的文本属性是不正确的。

private var action: UIAlertAction!

@IBAction func addSourceTapped(_ sender: Any) {

    ////////

    let alert = UIAlertController(title: "Add a News Source", message: nil, preferredStyle: .alert)

    alert.addTextField { (textField) in
        textField.placeholder = "Name"
        textField.addTarget(self, action: #selector(self.textFieldDidChange(_:)), for: .editingChanged) // <---
    }

    action = UIAlertAction(title: "Add", style: .default) { (_) in
        /////
    }
    action.isEnabled = false
    alert.addAction(action)

    ////////
}

@objc private func textFieldDidChange(_ field: UITextField) {
    action.isEnabled = field.text?.count ?? 0 > 0
}

Answer 4

使用动作的程序化解决方案。在课堂上添加按钮，并根据文本字段中的更改继续更改其状态。

import UIKit

final class ViewWithConfirmationController: UIViewController {
  private let askButton = UIButton()
  private let deleteAction = UIAlertAction(
    title: "Confirm",
    style: .default
  ) { _ in
    // Confirmed
  }

  init() {
    super.init(nibName: nil, bundle: nil)

    view.addSubview(askButton)

    askButton.setTitle("Call alert", for: .normal)
    askButton.addTarget(
      self,
      action: #selector(callAlert),
      for: .touchUpInside
    )
  }

  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  @objc func callAlert() {
    let alert = UIAlertController(
      title: "Confirmation alert",
      message: """
        Do you really want to do that?

        Please type in the magic word to confirm.
      """,
      preferredStyle: .alert
    )

    alert.addTextField { textField in
      textField.placeholder = "Magic word"
      textField.addTarget(
        self,
        action: #selector(self.textFieldDidChange(_:)),
        for: .editingChanged
      )
    }

    alert.addAction(
      UIAlertAction(
        title: "Cancel",
        style: .cancel,
        handler: { _ in }
      ))

    alert.addAction(deleteAction)

    // Confirm button will disabled until user type current organisation name
    deleteAction.isEnabled = false

    present(alert, animated: true, completion: nil)
  }

  @objc private func textFieldDidChange(_ field: UITextField) {
    guard let text = field.text else {
      print("Can't get text from text field in \(#function)")
      return
    }
    deleteAction.isEnabled = !text.isEmpty
  }
}

如何根据UITextField禁用UIAlertAction？

4 个答案: