在键盘上查看响应并隐藏iOS Swift 4

这是我的观点。

当我在文本视图中单击时,键盘就在上面。所以我添加了makea类,在那个类中,我添加了这些函数。

    var objectObserver:UIViewController?

    func setKeyboardResponsiviness(observer:UIViewController){
            objectObserver = observer
            NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)

                NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
        }

        @objc func keyboardWillShow(notification: NSNotification) {
            if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
                if objectObserver!.view.frame.origin.y == 0 {
                    objectObserver!.view.frame.origin.y -= keyboardSize.height
                }
            }
        }

        @objc func keyboardWillHide(notification: NSNotification) {
            if objectObserver!.view.frame.origin.y != 0 {
                objectObserver!.view.frame.origin.y = 0
            }
        } 

添加代码后,整个屏幕向上滑动,这是预期的目标,但作为副作用,有一半的文本视图不在屏幕上。我知道怎么修这个吗?