键盘将显示未称为iOS 12的通知

Question

在我的应用中，我希望收到UIResponder.keyboardWillShowNotification的通知，以更新我的文本字段的y位置。它在iOS 12之前运行；现在，它在我的一个视图控制器中没有被调用（它在其他控制器中起作用）。这是我执行此操作的代码：

@objc func keyboardWillShow(_ notification: Notification) {
    print("keyboard will show 2")
    guard let frameValue: NSValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else {
        return
    }
    let keyboardFrame = frameValue.cgRectValue
    UIView.animate(withDuration: animationTime) {
        self.addViewBottomConstraint.constant = keyboardFrame.size.height
        self.view.layoutIfNeeded()
        print("Bottom contraint height = \(self.addViewBottomConstraint.constant)")
    }
}

@objc func keyboardWillHide(_ notification: Notification) {
    UIView.animate(withDuration: animationTime) {
        self.addViewBottomConstraint.constant = 0
        self.view.layoutIfNeeded()
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

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

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

这里，“键盘将显示2”没有被打印，但是为其他具有相同通知的视图控制器打印。 iOS 12中有什么新原因导致此问题吗？否则，是否有不被调用的特定原因？谢谢你的帮助。

Answer 1

我一直在处理相同的问题。我在应用程序的第一个ViewController中运行以下代码。然后，通过获取我们保存在UserDefaults中的键盘高度值，可以在整个应用程序中使用它。它基本上是在屏幕上添加一个文本字段，并在获得键盘高度后立即将其隐藏。

如果您需要根据键盘高度绘制第一个窗口您无需调用t.resignFirstResponder（）和t.removeFromSuperview（）

这至少适用于iOS 12和13：

var t = UITextField()
let keyboardHeightKey = "keyboardHeight"

override func viewDidAppear(_ animated: Bool) {

    let keyboardHeightUserDefault = UserDefaults.standard.double(forKey: keyboardHeightKey)
    print("userdefault keyboard height: \(keyboardHeightUserDefault)")
    if keyboardHeightUserDefault == 0.0 {
        print("keyboard height is 0.0")
        keyboardStuff()
    }
    else {
        keyboardHeight = CGFloat(keyboardHeightUserDefault)
        print("keyboard height is \(keyboardHeight)")
    }
}

@objc func keyboardWillShow(_ notification: NSNotification) {
    print("keyboardWillShow")
    let kh = UserDefaults.standard.double(forKey: keyboardHeightKey)

    if kh == 0.0 {
        if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            let keyboardH = keyboardSize.height
            print("keyboardHeight: \(keyboardH)")
            keyboardHeight = keyboardH
            UserDefaults.standard.set(keyboardH, forKey: keyboardHeightKey)
            UserDefaults.standard.synchronize()
        }
    }
    t.resignFirstResponder()
    t.removeFromSuperview()
    print("kh is: \(kh)")
}


func keyboardStuff() {
    print("inside keyboardStuff")
    t = UITextField(frame: CGRect(x: CGFloat(0), y: CGFloat(0), width: CGFloat(10), height: CGFloat(10)))
    t.delegate = self
    self.view.addSubview(t)
    let item = t.inputAssistantItem
    t.autocorrectionType = .no
    item.leadingBarButtonGroups = []
    item.trailingBarButtonGroups = []

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

    delay(0.1) {
        print("inside delay")
        t.resignFirstResponder()
        t.removeFromSuperview()
    }


    t.becomeFirstResponder()
    t.isHidden = true
}


func delay(_ delay:Double, closure:@escaping ()->()) {
    let when = DispatchTime.now() + delay
    DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}