当尝试更改UIAlertController的消息颜色时，应用程序崩溃了

Question

我在尝试更改UIAlertController内的文字颜色时遇到了错误：

  

由于未捕获的异常而终止应用   'NSInvalidArgumentException'，原因：' - [NSConcreteAttributedString   rangeOfCharacterFromSet：]：发送到实例的无法识别的选择器   0x60000003e320'

尝试更改颜色的功能：

@objc private func submitScore(color: Bool = false) {
    var mess = ""
    mess = color ? "Invalid username" : ""
    let alertController = UIAlertController.init(title: "Submit score", message: mess, preferredStyle: .alert)
    alertController.setValue(NSAttributedString(string: mess, attributes: [NSForegroundColorAttributeName: UIColor.red]), forKey: "message")


    //Submit button calls function again
    let submit = UIAlertAction(title: "Submit", style: .default) { (submit) in
        self.submitScore(color: true)
    }
    let cancel = UIAlertAction(title: "Cancel", style: .cancel, handler: { (cancel) in

    })
    alertController.addTextField(configurationHandler: {(textfield) in
        textfield.placeholder = "Nickname"
    })
    alertController.addAction(submit)
    alertController.addAction(cancel)

    present(alertController, animated: true, completion: {(alertController) in
        print("shown")
    })
}

如果我删除第5行，问题就解决了。NSForegroundColorAttributeName是一个有效的NSAttributedString属性，所以我不明白错误..

Answer 1

message课程中没有关键名称为UIAlertController的可用属性，在这个位置使用attributedMessage来更改消息。

在这个地方

   let alertController = UIAlertController.init(title: "Submit score", message: mess, preferredStyle: .alert)
  alertController.setValue(NSAttributedString(string: mess, attributes: [NSForegroundColorAttributeName: UIColor.red]), forKey: "message")

使用

let alertController = UIAlertController.init(title: "Submit score", message: mess, preferredStyle: .alert)
alertController.setValue(NSAttributedString(string: mess, attributes: [NSForegroundColorAttributeName: UIColor.red]), forKey: "attributedMessage")

如果你想更改UIAlertController的标题，那么你应该使用'attributionTitle'键。

你得到了

的输出

Answer 2

 @objc private func submitScore(color: Bool = false) {
    var mess = ""
    mess = color ? "Invalid username" : ""
    let alertController = UIAlertController.init(title: "Submit score", message: mess, preferredStyle: .alert)

    //Submit button calls function again
    let submit = UIAlertAction(title: "Submit", style: .default) { (submit) in
        self.submitScore(color: true)
    }
    let cancel = UIAlertAction(title: "Cancel", style: .cancel, handler: { (cancel) in

    })
    alertController.addTextField(configurationHandler: {(textfield) in
        textfield.placeholder = "Nickname"
    })
    alertController.addAction(submit)
    alertController.addAction(cancel)

    present(alertController, animated: true, completion: {(alertController) in
        print("shown")
    })

    alertController.setValue(NSAttributedString(string: mess, attributes: [NSForegroundColorAttributeName: UIColor.red]), forKey: "message")

}

Answer 3

您似乎尝试将NSAttributedString设置为String变量message。试试https://stackoverflow.com/a/42118706/7064692