如何正确确定 iOS 上的键盘和文本字段位置？

Question

当键盘显示并且文本字段变得不可见时，我想提升视图。这是我的代码：

@objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        let tfPos = lastTextField!.convert(lastTextField!.frame, to: self.view)
        let tfBottom = tfPos.origin.y
        let kbTop = keyboardSize.origin.y

        if kbTop < tfBottom {
            self.verticalCenterConstraint.constant = -(tfBottom - kbTop)
        }
    }
}

我确定键盘的顶部，然后是文本字段的底部。但是，文本字段位置不正确，即使我可以在屏幕上清楚地看到它在键盘上方，我的代码说它在 35pt 下方。我该如何解决这个问题？

Answer 1

如果对约束进行了任何更改，则需要调用 self.view.layoutIfNeeded()。 你可以在动画块中调用它

UIView.animate(withDuration: 持续时间, 延迟：时间间隔（0）， 选项：动画曲线， 动画：{ self.view.layoutIfNeeded() }， 完成：无）

Answer 2

步骤：- 1 为隐藏和显示通知添加观察者

let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), 
name: Notification.Name.UIKeyboardWillHide, object: nil)
notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), 
name: Notification.Name.UIKeyboardWillChangeFrame, object: nil)

步骤：- 2 实现目标方法

@objc func adjustForKeyboard(notification: Notification) {
let userInfo = notification.userInfo!

let keyboardScreenEndFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
let keyboardViewEndFrame = view.convert(keyboardScreenEndFrame, from: view.window)

if notification.name == Notification.Name.UIKeyboardWillHide {
    yourTextView.contentInset = UIEdgeInsets.zero
} else {
    yourTextView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: keyboardViewEndFrame.height, right: 0)
}

yourTextView.scrollIndicatorInsets = yourTextView.contentInset

let selectedRange = yourTextView.selectedRange
yourTextView.scrollRangeToVisible(selectedRange)
}