【问题标题】：NSNotificationCenter Swift 3.0 on keyboard show and hideNSNotificationCenter Swift 3.0 上的键盘显示和隐藏
【发布时间】：2017-06-02 18:41:00
【问题描述】：

我正在尝试在键盘显示和消失时运行一个函数并具有以下代码：

let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #selector(ViewController.keyBoardUp(Notification :)), name:  NSNotification.Name.UIKeyboardWillShow, object: nil)

以及下面的函数keyBoardUp：

func keyBoardUp( Notification: NSNotification){
    print("HELLO")
}

但是，当键盘显示时，该功能不会打印到控制台。非常感谢您的帮助

【问题讨论】：

将选择器更改为#selector(ViewController.keyBoardUp(notification:)) 并将函数更改为func keyBoardUp( notification: Notification){ print("HELLO") }
Swift 3 NSNotificationCenter Keyboardwillshow/hide的可能重复
在 swift 3 中，您不应该在函数中遇到编译器错误吗？

标签： ios swift keyboard-events nsnotificationcenter

【解决方案1】：

斯威夫特 3：

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: Notification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: Notification.Name.UIKeyboardWillHide, object: nil)

}

func keyboardWillShow(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        print("notification: Keyboard will show")
        if self.view.frame.origin.y == 0{
            self.view.frame.origin.y -= keyboardSize.height
        }
    }

}

func keyboardWillHide(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0 {
            self.view.frame.origin.y += keyboardSize.height
        }
    }
}

斯威夫特 4.2.1：

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

@objc fileprivate func keyboardWillShow(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        // Do something with size
    }
}

@objc fileprivate func keyboardWillHide(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        // Do something with size
    }
}

Swift 4.2+

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)

}

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

}

@objc func keyboardWillHide(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0 {
            self.view.frame.origin.y += keyboardSize.height
        }
    }
}

【讨论】：

此代码将失败，键盘处于活动状态，键入任何内容，不要退出并按下 iphone 的锁定按钮，然后稍后解锁您的 iphone，您的视图将不可见
我通过硬编码keyboardSize.height来解决这个问题（因为我不想将整个视图移动到键盘的高度，因为它只是部分覆盖了预期的区域。所以而不是那部分你可以输入一个 Int
使用 UIKeyboardFrameEndUserInfoKey 获得正确的高度，在 iPad 上有不同的键盘高度（带或不带硬件键盘） - 对高度进行硬编码会导致问题。

【解决方案2】：

斯威夫特 4.2+

@vandana's 答案已更新以反映更改到 Swift 4.2 中的原生通知。

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)

}

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

}

@objc func keyboardWillHide(notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0 {
            self.view.frame.origin.y += keyboardSize.height
        }
    }
}

此外，您需要使用 UIKeyboardFrameEndUserInfoKey 来说明 iOS 11 引入的 safeAreaInset 更改。

【讨论】：

是 UIResponder.keyboardWillHideNotification 通知名称
我也需要函数上的@objc 关键字。
@RobEllis 是的，这些都是 Swift 4+ 所必需的。感谢您指出:)
记得在 viewWillAppear 中添加你的观察者并在 viewWillDisappear 中移除它们
@AmeyaVichare stackoverflow.com/a/36822456/7734643

【解决方案3】：

在

中设置键盘通知观察器

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardNotification(notification:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
}

并在你的函数中处理它

func keyboardNotification(notification: NSNotification) {
  print("keyboard displayed!!")
}

希望这会对你有所帮助。

【讨论】：

【解决方案4】：

斯威夫特 4.X / 5

我喜欢内联的、基于块的方法，它已经存在很长时间了！你可以阅读更多关于addObserver(...)here的参数。

这种方法的一些优点是：

您不需要使用@objc 关键字
您在设置观察者的同一位置编写回调代码

重要提示：在您设置的对象的deinit 中调用NotificationCenter.default.removeObserver(observer) 注册观察者（通常是视图控制器）。

let center = NotificationCenter.default

let keyboardWillShowObserver: NSObjectProtocol = center.addObserver(forName: UIResponder.keyboardWillShowNotification, object: nil, queue: nil) { (notification) in
    guard let value = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    let height = value.cgRectValue.height

    // use the height of the keyboard to layout your UI so the prt currently in
    // foxus remains visible
}

let keyboardWillHideObserver: NSObjectProtocol = center.addObserver(forName: UIResponder.keyboardWillHideNotification, object: nil, queue: nil) { (notification) in

    // restore the layout of your UI before the keyboard has been shown
}

【讨论】：

【解决方案5】：

为 swift 更新：

// MARK:- Kyeboard hide/show methods

func keyboardWasShown(_ notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y == 0{
            self.view.frame.origin.y -= keyboardSize.height
        }
    }
}

func keyboardWillBeHidden(_ notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0{
            self.view.frame.origin.y += keyboardSize.height
        }
    }
}

func registerForKeyboardNotifications(){
    //Adding notifies on keyboard appearing
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWasShown(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)

    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillBeHidden(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

func deregisterFromKeyboardNotifications(){
    //Removing notifies on keyboard appearing
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

func textFieldDidBeginEditing(_ textField: UITextField) {
    if textField == mEnterPasswordTextField || textField == mEnterConfirmPassword  {
            animateViewMoving(up: true, moveValue: 120)
    }
}

func textFieldDidEndEditing(_ textField: UITextField) {
    if textField == mEnterPasswordTextField || textField == mEnterConfirmPassword  {
            animateViewMoving(up: false, moveValue: 120)
    }
}

func animateViewMoving (up:Bool, moveValue :CGFloat){
    let movementDuration:TimeInterval = 0.3
    let movement:CGFloat = ( up ? -moveValue : moveValue)
    UIView.beginAnimations( "animateView", context: nil)
    UIView.setAnimationBeginsFromCurrentState(true)
    UIView.setAnimationDuration(movementDuration )
    self.view.frame = self.view.frame.offsetBy(dx: 0,  dy: movement)
    UIView.commitAnimations()
}

//在viewDidLoad()中

self.registerForKeyboardNotifications()
self.deregisterFromKeyboardNotifications()

【讨论】：

【解决方案6】：

KeyBoard 将在 Swift 4 中使用 TxtField 显示和隐藏

class ViewController: UIViewController {


@IBOutlet weak var commentsTxt: UITextField!
@IBOutlet weak var keyboardBottom: NSLayoutConstraint!

override func viewWillAppear(_ animated: Bool) {
    IQKeyboardManager.shared.enable = false
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(keyboardWillShow),
        name: UIResponder.keyboardWillShowNotification,
        object: nil
    )
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(keyboarddidHide),
        name: UIResponder.keyboardWillHideNotification,
        object: nil
    )
}

@objc func keyboardWillShow(_ notification: Notification) {
    if let keyboardFrame: NSValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue {
        let keyboardRectangle = keyboardFrame.cgRectValue
        let keyboardHeight = keyboardRectangle.height
        self.keyboardBottom.constant = keyboardHeight - self.bottomLayoutGuide.length
        DispatchQueue.main.asyncAfter(deadline: .now()+0.1, execute: {
            let bottomOffset = CGPoint(x: 0, y: self.scrlView.contentSize.height - self.scrlView.bounds.size.height)
            self.scrlView.setContentOffset(bottomOffset, animated: true)
        })
    }
}
@objc func keyboarddidHide(_ notification: Notification) {
    self.keyboardBottom.constant = 0
    
}

   override func viewWillDisappear(_ animated: Bool) {
    IQKeyboardManager.shared.enable = true
     NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillHideNotification, object: nil)
}

}

【讨论】：

【解决方案7】：

试试这个

 override func viewDidLoad()
    {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(notification:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(notification:)), name: NSNotification.Name.UIKeyboardDidHide, object: nil)
}

 @objc func keyboardWillShow(notification: NSNotification) {
      if(messageCount > 0)
      {
        tableView.scrollToRow(at: IndexPath(item:messageCount - 1, section: 0), at: .bottom, animated: true)
      }
}

@objc func keyboardWillHide(notification: NSNotification) {
    if(messageCount > 0)
    {
        tableView.scrollToRow(at: IndexPath(item:0, section: 0), at: .top, animated: true)
    }
}

【讨论】：

【解决方案8】：

斯威夫特 4.2

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

@objc func didReceiveKeyboardNotificationObserver(_ notification: Notification) {
    let userInfo = notification.userInfo
    let keyboardBounds = (userInfo!["UIKeyboardBoundsUserInfoKey"] as! NSValue).cgRectValue
    let keyboardFrame = (userInfo!["UIKeyboardFrameEndUserInfoKey"] as! NSValue).cgRectValue
    let duration = userInfo!["UIKeyboardAnimationDurationUserInfoKey"] as! Double
    let curve = userInfo!["UIKeyboardAnimationCurveUserInfoKey"] as! Int
    let frameBegin = (userInfo!["UIKeyboardFrameBeginUserInfoKey"] as! NSValue).cgRectValue
    let centerBegin = (userInfo!["UIKeyboardCenterBeginUserInfoKey"] as! NSValue).cgPointValue
    let center = (userInfo!["UIKeyboardCenterEndUserInfoKey"] as! NSValue).cgPointValue
    let location = userInfo!["UIKeyboardIsLocalUserInfoKey"] as! Int
    println("keyboardBounds: \(keyboardBounds) \nkeyboardFrame: \(keyboardFrame) \nduration: \(duration) \ncurve: \(curve) \nframeBegin:\(frameBegin) \ncenterBegin:\(centerBegin)\ncenter:\(center)\nlocation:\(location)")
    switch notification.name {
    case UIResponder.keyboardWillShowNotification:
    // keyboardWillShowNotification
    case UIResponder.keyboardWillHideNotification:
    // keyboardWillHideNotification
    default:
        break
    }
}

【讨论】：

【解决方案9】：

斯威夫特 4.2

此版本适用于 iPhone 5 和 iPhone X。如果您在约束设置期间尊重安全区域，它会非常有效。

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)
}

@objc func keyboardWillShow(notification: NSNotification) {
        if let _ = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
            self.view.frame.origin.y = self.navigationController!.navigationBar.frame.size.height + UIApplication.shared.statusBarFrame.size.height
            if self.emailTextField.isFirstResponder {
                self.view.frame.origin.y -= 100
            } else if self.passwordTextField.isFirstResponder {
                self.view.frame.origin.y -= 150
            } else if self.passwordConfirmTextField.isFirstResponder {
                self.view.frame.origin.y -= 200
            }
        }
}

@objc func keyboardWillHide(notification: NSNotification) {
        if self.view.frame.origin.y != 0 {
           self.view.frame.origin.y = self.navigationController!.navigationBar.frame.size.height + UIApplication.shared.statusBarFrame.size.height
        }
}

【讨论】：

【解决方案10】：

斯威夫特 > 4.++

您可以使用协议和协议扩展。让我们创建 KeyboardListener 协议

protocol KeyboardListener: class {
   func registerKeyboardObserver()
   func keyboardDidUpdate(keyboardHeight: CGFloat)
   func removeObserver()
}

然后在 UIViewController 扩展中创建 @objc 函数

extension UIViewController {
@objc func adjustForKeyboard(notification: Notification) {
    guard let keyboardValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
    
    let keyboardScreenEndFrame = keyboardValue.cgRectValue
    let keyboardViewEndFrame = view.convert(keyboardScreenEndFrame, from: view.window)
    
    if notification.name == UIResponder.keyboardWillHideNotification {
        if let keyboardLister = self as? KeyboardListener {
            keyboardLister.keyboardDidUpdate(keyboardHeight: .zero)
        }
    } else {
        if let keyboardLister = self as? KeyboardListener {
            keyboardLister.keyboardDidUpdate(keyboardHeight: keyboardViewEndFrame.height - view.safeAreaInsets.bottom)
        }
    }
}

}

然后，为默认实现使用键盘侦听器扩展

extension KeyboardListener where Self: UIViewController {
func registerKeyboardObserver() {
    let notificationCenter = NotificationCenter.default
    notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), name: UIResponder.keyboardWillHideNotification, object: nil)
    notificationCenter.addObserver(self, selector: #selector(adjustForKeyboard), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
}

func removeObserver() {
    NotificationCenter.default.removeObserver(self)
}

}

最后，我们可以在 ViewController 类中使用它

extension EditProfileVC: KeyboardListener {
func keyboardDidUpdate(keyboardHeight: CGFloat) {
    //update view when keyboard appear, 
}

}

并从 viewwillAppear 调用 register 并从 deinit 调用 removeObserver

 override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    registerKeyboardObserver()
}

deinit {
   removeObserver()
}

【讨论】：