如何检测键盘何时显示和隐藏

时间：2010-12-07 07:57:23

标签： ios iphone iphone-sdk-3.0

如何检测键盘何时显示并隐藏在我的应用程序中？

14 个答案:

答案 0 :(得分：159)

在您的类的ViewDidLoad方法中设置以侦听有关键盘的消息：

// Listen for keyboard appearances and disappearances
[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardDidShow:)
                                             name:UIKeyboardDidShowNotification
                                           object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardDidHide:)
                                             name:UIKeyboardDidHideNotification
                                           object:nil];

然后在您指定的方法中（在本例中为keyboardDidShow和keyboardDidHide），您可以对此采取一些措施：

- (void)keyboardDidShow: (NSNotification *) notif{
    // Do something here
}

- (void)keyboardDidHide: (NSNotification *) notif{
    // Do something here
}

答案 1 :(得分：82)

您可能只需要addObserver中的viewDidLoad。但是addObserver中的viewWillAppear和removeObserver中的viewWillDisappear可以防止您在更改视图时发生的罕见崩溃。

Swift 4.2 

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillDisappear), name: UIResponder.keyboardWillHideNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillAppear), name: UIResponder.keyboardWillShowNotification, object: nil)
}

@objc func keyboardWillAppear() {
    //Do something here
}

@objc func keyboardWillDisappear() {
    //Do something here
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self)
}

Swift 3和4 

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillDisappear), name: Notification.Name.UIKeyboardWillHide, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillAppear), name: Notification.Name.UIKeyboardWillShow, object: nil)
}

@objc func keyboardWillAppear() {
    //Do something here
}

@objc func keyboardWillDisappear() {
    //Do something here
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self)
}

较旧的斯威夫特

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

    NSNotificationCenter.defaultCenter().addObserver(self, selector:"keyboardWillAppear:", name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector:"keyboardWillDisappear:", name: UIKeyboardWillHideNotification, object: nil)
}

func keyboardWillAppear(notification: NSNotification){
    // Do something here
}

func keyboardWillDisappear(notification: NSNotification){
    // Do something here
}

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

答案 2 :(得分：18)

斯威夫特3：

NotificationCenter.default.addObserver(self, selector: #selector(viewController.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(viewController.keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)

func keyboardWillShow(_ notification: NSNotification){
    // Do something here
}

func keyboardWillHide(_ notification: NSNotification){
    // Do something here
}

答案 3 :(得分：7)

雨燕5

上面的答案是正确的。尽管我希望创建一个帮助程序来包装notification's observers。

好处：

  1. 您不必在每次处理键盘行为时都重复操作。
  2. 您可以通过实现其他枚举值来扩展其他通知
  3. 当您需要在多个控制器中处理键盘时，这很有用。

示例代码：

extension KeyboardHelper {
    enum Animation {
        case keyboardWillShow
        case keyboardWillHide
    }

    typealias HandleBlock = (_ animation: Animation, _ keyboardFrame: CGRect, _ duration: TimeInterval) -> Void
}

final class KeyboardHelper {
    private let handleBlock: HandleBlock

    init(handleBlock: @escaping HandleBlock) {
        self.handleBlock = handleBlock
        setupNotification()
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    private func setupNotification() {
        _ = NotificationCenter.default
            .addObserver(forName: UIResponder.keyboardWillShowNotification, object: nil, queue: .main) { [weak self] notification in
                self?.handle(animation: .keyboardWillShow, notification: notification)
            }

        _ = NotificationCenter.default
            .addObserver(forName: UIResponder.keyboardWillHideNotification, object: nil, queue: .main) { [weak self] notification in
                self?.handle(animation: .keyboardWillHide, notification: notification)
            }
    }

    private func handle(animation: Animation, notification: Notification) {
        guard let userInfo = notification.userInfo,
            let keyboardFrame = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
            let duration = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double
        else { return }

        handleBlock(animation, keyboardFrame, duration)
    }
}

使用方法：

private var keyboardHelper: KeyboardHelper?
...

override func viewDidLoad() {
   ...
   keyboardHelper = KeyboardHelper { [unowned self] animation, keyboardFrame, duration in
        switch animation {
        case .keyboardWillShow:
            print("keyboard will show")
        case .keyboardWillHide:
            print("keyboard will hide")
        }
    }

}

答案 4 :(得分：6)

斯威夫特4：

  NotificationCenter.default.addObserver( self, selector: #selector(ControllerClassName.keyboardWillShow(_:)),
  name: Notification.Name.UIKeyboardWillShow,
  object: nil)
  NotificationCenter.default.addObserver(self, selector: #selector(ControllerClassName.keyboardWillHide(_:)),
  name: Notification.Name.UIKeyboardWillHide,
  object: nil)

接下来，添加方法以在对象的生命结束时停止侦听通知： - 

Then add the promised methods from above to the view controller:
deinit {
  NotificationCenter.default.removeObserver(self)
}
func adjustKeyboardShow(_ open: Bool, notification: Notification) {
  let userInfo = notification.userInfo ?? [:]
  let keyboardFrame = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
  let height = (keyboardFrame.height + 20) * (open ? 1 : -1)
  scrollView.contentInset.bottom += height
  scrollView.scrollIndicatorInsets.bottom += height
}

@objc func keyboardWillShow(_ notification: Notification) {
  adjustKeyboardShow(true, notification: notification)
}
@objc func keyboardWillHide(_ notification: Notification) {
  adjustKeyboardShow(false, notification: notification)
}

答案 5 :(得分：4)

查看“文本，网页和编辑编程指南”的Managing the Keyboard部分，了解有关跟踪显示或隐藏键盘的信息，以及如何手动显示/关闭它。

答案 6 :(得分：4)

您需要为2个键盘通知注册自己：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardDidShow:) name: UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector (keyboardDidHide:) name: UIKeyboardDidHideNotification object:nil];

关于如何将TextField调整为键盘的精彩帖子 - http://iosdevelopertips.com/user-interface/adjust-textfield-hidden-by-keyboard.html

答案 7 :(得分：4)

斯威夫特 - 4 

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

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self) //remove observer
}

func addKeyBoardListener() {
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil);
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil);
}

@objc func keyboardWillShow(_ notification: Notification) {

}

@objc func keyboardWillHide(_ notification: Notification) {

}

答案 8 :(得分：2)

Swift 4 - dd 20 october 2017 

override func viewDidLoad() {
    [..]

    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillDisappear(_:)), name: Notification.Name.UIKeyboardWillHide, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillAppear(_:)), name: Notification.Name.UIKeyboardWillShow, object: nil)
}

@objc func keyboardWillAppear(_ notification: NSNotification) {
    if let userInfo = notification.userInfo, 
       let keyboardFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue).cgRectValue {
           let inset = keyboardFrame.height // if scrollView is not aligned to bottom of screen, subtract offset
           scrollView.contentInset.bottom = inset
           scrollView.scrollIndicatorInsets.bottom = inset
    }
}

@objc func keyboardWillDisappear(_ notification: NSNotification) {
    scrollView.contentInset.bottom = 0
    scrollView.scrollIndicatorInsets.bottom = 0
}

deinit {
    NotificationCenter.default.removeObserver(self)
}

答案 9 :(得分：1)

如果您有多个UITextField，并且您需要在键盘出现或消失时（或之前）执行某些操作，则可以实施此方法。

将UITextFieldDelegate添加到您的班级。分配整数计数器，假设：

NSInteger editCounter;

在viewDidLoad的某处将此计数器设置为零。 然后，实施textFieldShouldBeginEditing和textFieldShouldEndEditing委托方法。

在第一个中，将1添加到editCounter。如果editCounter的值变为1 - 这意味着将出现键盘（如果您返回YES，则表示如果）。如果editCounter＆gt; 1 - 这意味着键盘已经可见，另一个UITextField保持焦点。

在textFieldShouldEndEditing中从editCounter中减去1。如果你得到零 - 键盘将被解除，否则它将保留在屏幕上。

答案 10 :(得分：1)

在Swift 4.2中，通知名称已移至其他名称空间。所以现在它了

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


override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self)
}



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

@objc private extension ClassName {

func keyboardWillShow(_ notification: Notification) {

}

func keyboardWillHide(_ notification: Notification) {

}
}

答案 11 :(得分：0)

您可以使用KBKeyboardObserver库。它包含一些示例并提供简单的界面。

答案 12 :(得分：0)

这里有一个CocoaPods可以帮助您在NSNotificationCentr上观察键盘的可见性：https://github.com/levantAJ/Keyhi

pod 'Keyhi'

答案 13 :(得分：0)

所以啊，这才是真正的答案。

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