在swift中的Alertview内创建和自定义UITextfield

我正在尝试在警报视图中创建一个大尺寸的文本字段，编程限制为100个字符。这是我的密码：

func alertWithTF() {
        let alert = UIAlertController(title: Constants.cancelPopupTitle,
                                      message: Constants.cancelPopupMessage,
                                      preferredStyle: .alert)
        alert.addTextField { (textField) in
            textField.frame = CGRect(x: 20, y: 100, width: 300, height: 80)
            textField.placeholder = "Please enter message"
            textField.borderStyle = UITextField.BorderStyle.line
            textField.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
        }
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak alert] (_) in
            guard let textfield = alert?.textFields?.first else { return }
            let message = textfield.text ?? ""
            print(message)
        }))
        alert.addAction(UIAlertAction(title: "Cancel", style: .cancel))
        self.present(alert, animated: true, completion: nil)
}

以下是我的问题：

• 我想通过编辑文本字段的框架来修改文本字段的高度，但它似乎不起作用
• 我还想设置textfield的限制字符
• UIAlertController是不可自定义的。您可以为此情况创建自己的alertViewController，然后根据需要使用UI

• 在addTextfield中，提供委托给self

    alert.addTextField { (textField) in
  
      textField.frame = CGRect(x: 20, y: 100, width: 300, height: 80)
      textField.placeholder = "Please enter message"
      textField.borderStyle = UITextField.BorderStyle.line
      textField.delegate = self
      textField.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
  }
  

您可以使用shouldChangeCharacters方法来限制长度

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let maxLimit = 180
let currentString = textField.text!
let newString: String =
    currentString.replacingCharacters(in: range, with: string) as String
return newString.length <= maxLength
}

---

因此，在我自己进行了几次研究之后，我成功地实现了这一点：

extension ViewController: UITextViewDelegate {
    func alertWithTF() {
        let alert = UIAlertController(title: "Title",
                                      message: "\n\n\n\n\n",
                                      preferredStyle: .alert)
        let textView = UITextView()
        textView.borderColor = .black
        textView.borderWidth = 1.0
        textView.delegate = self
        textView.text = Constants.textViewPlaceholder
        textView.textColor = .lightGray
        alert.view.addSubview(textView)

        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.topAnchor.constraint(equalTo: alert.view.topAnchor, constant: 125).isActive = true
        textView.rightAnchor.constraint(equalTo: alert.view.rightAnchor, constant: -20).isActive = true
        textView.leftAnchor.constraint(equalTo: alert.view.leftAnchor, constant: 20).isActive = true
        textView.bottomAnchor.constraint(equalTo: alert.view.bottomAnchor, constant: -60).isActive = true
        textView.heightAnchor.constraint(equalToConstant: 60).isActive = true

        alert.view.translatesAutoresizingMaskIntoConstraints = false

        alert.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { [weak self] (_) in
            self?.dismiss(animated: true, completion: nil)
        }))

        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak self] (_) in
            let message = (textView.text == nil||textView.text == Constants.textViewPlaceholder ? "" : textView.text)
            print(message)
        }))

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

因此，我创建了一个TextView而不是TextField，并在alertView中为其设置了约束。这些代码并不完美，但运行良好。我还使用TextView委托处理TextView字符限制和占位符，因为UITextView不支持它：

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        let newText = (textView.text as NSString).replacingCharacters(in: range, with: text)
        let numberOfChars = newText.count
        return numberOfChars < 101 //Max 100 chars
    }

    func textViewDidBeginEditing(_ textView: UITextView) {
        if textView.textColor == UIColor.lightGray {
            textView.text = ""
            textView.textColor = UIColor.black
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
        if textView.text == "" {
            textView.text = Constants.textViewPlaceholder
            textView.textColor = UIColor.lightGray
        }
    }

func textView（textView:UITextView，shouldChangeTextIn范围：NSRange，replacementText:String）->Bool{
让newText=（textView.text作为NSString）。replacingCharacters（在：范围内，使用：text）
设numberOfChars=newText.count
返回字符数<101//最多100个字符
}
func textViewDidBeginEditing（uTEXTVIEW:UITextView）{
如果textView.textColor==UIColor.lightGray{
textView.text=“”
textView.textColor=UIColor.black
}
}
func textViewDidEndEditing（uTEXTVIEW:UITextView）{
如果textView.text==“”{
textView.text=Constants.textViewPlaceholder
textView.textColor=UIColor.lightGray
}
}

---

希望这是有帮助的
关于如何将文本字段限制为一定数量的字符，有很多资源。你找过了吗？另外，如果您最多使用100个字符，那么使用文本视图不是更好吗？大多数参考资料都告诉我使用“shouldChangeCharactersInRange”，但我不太明白它是如何工作的。是的，文本视图似乎更适合这种情况。谢谢你的建议！我知道一开始可能会有点难以承受。我自己也去过那里。关键是要有耐心，多读书。看很多例子。做很多POC。祝你好运谢谢你的详细回答！如果没有可行的解决方案，我将要创建自己的alertViewController。这将文本字段的高度限制为

100pts

，而不是

textField

中的字符计数。

extension ViewController: UITextViewDelegate {
    func alertWithTF() {
        let alert = UIAlertController(title: "Title",
                                      message: "\n\n\n\n\n",
                                      preferredStyle: .alert)
        let textView = UITextView()
        textView.borderColor = .black
        textView.borderWidth = 1.0
        textView.delegate = self
        textView.text = Constants.textViewPlaceholder
        textView.textColor = .lightGray
        alert.view.addSubview(textView)

        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.topAnchor.constraint(equalTo: alert.view.topAnchor, constant: 125).isActive = true
        textView.rightAnchor.constraint(equalTo: alert.view.rightAnchor, constant: -20).isActive = true
        textView.leftAnchor.constraint(equalTo: alert.view.leftAnchor, constant: 20).isActive = true
        textView.bottomAnchor.constraint(equalTo: alert.view.bottomAnchor, constant: -60).isActive = true
        textView.heightAnchor.constraint(equalToConstant: 60).isActive = true

        alert.view.translatesAutoresizingMaskIntoConstraints = false

        alert.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { [weak self] (_) in
            self?.dismiss(animated: true, completion: nil)
        }))

        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak self] (_) in
            let message = (textView.text == nil||textView.text == Constants.textViewPlaceholder ? "" : textView.text)
            print(message)
        }))

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

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        let newText = (textView.text as NSString).replacingCharacters(in: range, with: text)
        let numberOfChars = newText.count
        return numberOfChars < 101 //Max 100 chars
    }

    func textViewDidBeginEditing(_ textView: UITextView) {
        if textView.textColor == UIColor.lightGray {
            textView.text = ""
            textView.textColor = UIColor.black
        }
    }

    func textViewDidEndEditing(_ textView: UITextView) {
        if textView.text == "" {
            textView.text = Constants.textViewPlaceholder
            textView.textColor = UIColor.lightGray
        }
    }