ios - 我似乎无法让我的 KeyboardWillShow 工作？

Question

我的代码没有显示任何错误，但是当我启动模拟器时，应用程序崩溃了。我似乎找不到问题，但当我实现“keyboardWillShow”时它开始崩溃。

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    NotificationCenter.default.addObserver(
        self,
        selector: #selector(keyboardWillShow(with:)),
        name: UIResponder.keyboardWillShowNotification,
        object: nil)

}

// Mark: Actions

@objc func keyboardWillShow(with notification: Notification) {
    let key = "UIKeyboardFrameEndUserInfoKey"
    guard let keyboardFrame = notification.userInfo?[key] as? NSValue else { return }
    let keyboardHeight = keyboardFrame.cgRectValue.height

    buttomConstraint.constant = keyboardHeight

    UIView.animate(withDuration: 0.2) {
        self.view.layoutIfNeeded()
    }
}

Answer 1

Swift 4.2 中有一些变化。我不确定，但请在“keyboardWillShow”中尝试以下操作 - func:

let frameEndUserInfoKey = UIKeyboardFrameEndUserInfoKey
if let kbFrame = notification.userInfo?[frameEndUserInfoKey] as? CGRect {
    let keyboardHeight = kbFrame.size.height
    buttomConstraint.constant = keyboardHeight

    UIView.animate(withDuration: 0.2) {
        self.view.layoutIfNeeded()
    }
}