如何在Swift 3中编写键盘通知

Question

我正在尝试将此代码更新为swift 3：

NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)

NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)`

到目前为止，我刚刚尝试了编译器提供的自动更正。这导致代码如下：

let notificationCenter = NotificationCenter.default()
notificationCenter.addObserver(self, selector: Selector(("keyboardWillShow:")), name: NSNotification.Name.UIKeyboardWillShow, object: nil)

notificationCenter.addObserver(self, selector: Selector(("keyboardWillHide:")), name: NSNotification.Name.UIKeyboardWillHide, object: nil)`

不幸的是，这并没有让我走得太远，导致其他错误。

有人解决了吗？

请注意，我只是在尝试编写通知。我（还）没有尝试修复通知功能..谢谢

Answer 1

我通过编写像这样的代码来解决这个问题

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: .UIKeyboardWillShow, object: nil)

Answer 2

Swift 4.2 Xcode 10（10L213o）

与Swift 3相比，主要变化在于UIWindow. keyboardWillShowNotification和UIWindow.keyboardWillShowNotification

let notifier = NotificationCenter.default
notifier.addObserver(self,
                     selector: #selector(KeyboardLayoutConstraint.keyboardWillShowNotification(_:)),
                     name: UIWindow.keyboardWillShowNotification,
                     object: nil)
notifier.addObserver(self,
                     selector: #selector(KeyboardLayoutConstraint.keyboardWillHideNotification(_:)),
                     name: UIWindow.keyboardWillHideNotification,
                     object: nil)


@objc
func keyboardWillShowNotification(_ notification: NSNotification) {}

@objc
func keyboardWillHideNotification(_ notification: NSNotification) {}

Answer 3

Swift 4

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

func keyboardWillShow(notification: NSNotification) {
     print("keyboardWillShow")
}

func keyboardWillHide(notification: NSNotification){
     print("keyboardWillHide")
}

您还可以在这些方法内的代码下方获取键盘信息。

NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillChange), name: .UIKeyboardWillChangeFrame, object: nil) .      

@objc func keyboardWillChange(notification: NSNotification) {
     let duration = notification.userInfo![UIKeyboardAnimationDurationUserInfoKey] as! Double
     let curve = notification.userInfo![UIKeyboardAnimationCurveUserInfoKey] as! UInt
     let curFrame = (notification.userInfo![UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
     let targetFrame = (notification.userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
     let deltaY = targetFrame.origin.y - curFrame.origin.y
 }

Answer 4

对于Swift 4.2 x = [1,2,1,4,3,2,5,9] def counts(my_list): item_count = {} for item in my_list: item_count[item] = item_count.get(item,0)+1 return counts counts(x) 重命名为.UIKeyboardWillShow 和 UIResponder.keyboardWillShowNotification重命名为.UIKeyboardWillHide

UIResponder.keyboardWillHideNotification

Answer 5

您可以将已弃用的字符串文字Selector替换为经过类型检查的#selector(Class.method)对：

let center = NotificationCenter.default
center.addObserver(self,
                   selector: #selector(keyboardWillShow(_:)),
                   name: .UIKeyboardWillShow,
                   object: nil)

center.addObserver(self,
                   selector: #selector(keyboardWillHide(_:)),
                   name: .UIKeyboardWillHide,
                   object: nil)

#selector语法更安全，因为Swift能够在编译时检查指定的方法实际存在。

有关Swift选择器的更多信息，请参阅rickster's detailed answer。

Answer 6

在Swift 3.0中

 override func viewDidLoad()
    {
        super.viewDidLoad()
 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)

}

键盘显示和隐藏

func keyboardWillShow(notification: NSNotification) 
{

      // Your Code Here
}

func keyboardWillHide(notification: NSNotification)
{  
   //Your Code Here     
}

Answer 7

您可以分别在两个版本的Swift上执行键盘通知。

添加Objserver：

NotificationCenter.default.addObserver(self, selector: #selector(keyboardDidShow), name: .UIKeyboardWillShow, object: nil)

调用函数swift 3

func keyboardDidShow() {
          print("keyboardDidShow")
       }

调用函数在swift 4中

@objc func keyboardDidShow() {
      print("keyboardDidShow")
   }

Answer 8

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

Answer 9

Swift 5.1 +组合+ SwiftUI

@State var keyboardHeight: CGFloat = 0 // or @Published if one is in ViewModel: ObservableObject

private var cancellableSet: Set<AnyCancellable> = []

init() {

   let notificationCenter = NotificationCenter.default

   notificationCenter.publisher(for: UIWindow.keyboardWillShowNotification)
       .map {
             guard
                 let info = $0.userInfo,
                 let keyboardFrame = info[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect
                 else { return 0 }

             return keyboardFrame.height
         }
         .assign(to: \.keyboardHeight, on: self)
         .store(in: &cancellableSet)

     notificationCenter.publisher(for: UIWindow.keyboardDidHideNotification)
         .map { _ in 0 }
         .assign(to: \.keyboardHeight, on: self)
         .store(in: &cancellableSet)
    }

Answer 10

这是迄今为止对我最有效的解决方案（从“让Build That App” YouTube频道使用）

class ChatVC: UIViewController, UITableViewDelegate, UITableViewDataSource, UITextFieldDelegate {

// reference to your UIView with message TextField

    @IBOutlet weak var ChatView: UIView!   


// bottom constrain to your UIView (in my case ChatView)

    var bottomConstraint: NSLayoutConstraint?  

    override func viewDidLoad() {
        super.viewDidLoad()

// add some text in the placeholder if you want

        messageField.placeholder = "Type your message.." 

// here we add two notifications for showing and hiding the keyboard

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

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


// defines the start position for message textField that will be shown on the screen

        bottomConstraint = NSLayoutConstraint(item: ChatViewField!, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: -40)    
        view.addConstraint(bottomConstraint!)    
    }

// handles notifications for both cases when keyboard pops up and disappears  

  @objc func handleKeyboardNotification(notification: NSNotification){
        if let userInfo = notification.userInfo {

            let keyboardFrame =  (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
            print(keyboardFrame)

            let isKeyboardShowing = notification.name == UIResponder.keyboardWillShowNotification

            bottomConstraint?.constant = isKeyboardShowing ? -keyboardFrame.height : -40

// makes animation at the same time as the keyboard

UIView.animate(withDuration: 0, delay: 0, options: UIView.AnimationOptions.curveEaseOut, animations: {

                self.view.layoutIfNeeded()
            }) { (completed) in    
            }   
        }
    }