如何使用iOS上的约束将视图附加到键盘顶端

override func viewDidLoad() {
    super.viewDidLoad()
    
    // 注册键盘出现和消失的通知
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
}

deinit {
    // 移除键盘出现和消失的通知
    NotificationCenter.default.removeObserver(self)
}

@objc func keyboardWillShow(_ notification: Notification) {
    guard let userInfo = notification.userInfo,
          let keyboardFrame = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect
    else {
        return
    }
    
    // 获取键盘的高度
    let keyboardHeight = keyboardFrame.size.height
    
    // 更新视图的布局约束，将视图的底部与键盘的顶部对齐
    // NSLayoutConstraint是一种常用的布局约束类，可以用来设置视图的位置和大小
    NSLayoutConstraint.activate([
        yourView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -keyboardHeight)
    ])
}

@objc func keyboardWillHide(_ notification: Notification) {
    // 恢复视图原本的布局
    NSLayoutConstraint.deactivate([
        yourView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
    ])
}