如何检测键盘何时显示并隐藏在我的应用程序中？
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];
然后在你指定的方法（在本例中为keyboardDidShow和keyboardDidHide）中你可以做些什么：
- (void)keyboardDidShow: (NSNotification *) notif{
// Do something here
}
- (void)keyboardDidHide: (NSNotification *) notif{
// Do something here
}
在Swift 4.2中，通知名称已移至另一个名称空间。所以现在是
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 WhateverTheClassNameIs {
func keyboardWillShow(_ notification: Notification) {
// Do something here.
}
func keyboardWillHide(_ notification: Notification) {
// Do something here.
}
}
你可以使用KBKeyboardObserver库。它包含一些示例并提供简单的界面。
有一个CocoaPods便于在NSNotificationCentr观察键盘的可见性：https://github.com/levantAJ/Keyhi
pod 'Keyhi'
你可能只需要在addObserver中使用viewDidLoad。但是在addObserver中使用viewWillAppear和在removeObserver中使用viewWillDisappear可以防止在您改变观点时发生的罕见崩溃。
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)
}
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)
}
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)
}
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
}
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)
}
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) {
}
查看“文本，Web和编辑编程指南”的Managing the Keyboard部分，了解有关跟踪显示或隐藏的键盘以及如何手动显示/关闭键盘的信息。
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调整到键盘的好文章 - http://iosdevelopertips.com/user-interface/adjust-textfield-hidden-by-keyboard.html
斯威夫特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)
}
如果你有一个以上的UITextFields并且你需要在键盘出现或消失时（或之前）做某事，你可以实现这种方法。
将UITextFieldDelegate添加到您的班级。分配整数计数器，让我们说：
NSInteger editCounter;
在viewDidLoad的某个地方将此计数器设置为零。然后，实现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> 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。