iOS Swift检测键盘事件

Question

我可以以某种方式检测来自iOS键盘的事件吗？

我想检测UIViewController上没有UITextField或任何此类对象的此类事件。

我只有四个UIView的圆圈，当按下键盘上的按钮时，我想用不同的颜色绘制它们。

Answer 1

您没有任何对象从键盘获取输入。要使键盘出现，您的视图中必须包含UITextField或UITextView对象。

但这是检测视图控制器中键盘事件的过程。您可以在视图控制器上设置观察者以获取键盘通知。

要在swift 3中注册键盘通知，请在视图控制器的viewDidLoad（）或viewWillAppear（）方法中使用write这些行

    NotificationCenter.default.addObserver(self, selector: #selector(keyBoardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyBoardWillHide(notification:)), name: .UIKeyboardWillHide, object: nil)

然后在视图控制器中实现两个方法keyBoardWillHide（:)和keyBoardWillShow（:)方法

    func keyBoardWillShow(notification: NSNotification) {
            //handle appearing of keyboard here
    }


    func keyBoardWillHide(notification: NSNotification) {
              //handle dismiss of keyboard here
     }

Answer 2

您可以使用键盘处理程序

创建自己的视图

//Example
class CustomKeyInput: UIControl, UIKeyInput{
    //UIKeyInput
    public var hasText: Bool { return false }
    public func insertText(_ text: String){
        print(#function)
        print(text)
        print(text.characters.count)
    }
    public func deleteBackward(){
        print(#function)
    }

    //UIControl
    override var canBecomeFirstResponder: Bool {return true}
}


//Usage
class ViewController: UIViewController {

    @IBOutlet weak var keyView: CustomKeyInput!

    override func viewDidAppear(_ animated: Bool) {
        keyView.becomeFirstResponder()
    }
}

Answer 3

Swift 4.2

注册活动：

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

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

选择器：

@objc func keyboardWillShow(notification: NSNotification) {
   let keyboardHeight = (notification.userInfo![UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
   print(keyboardHeight)
}

@objc func keyboardWillHide(notification: NSNotification) {
   let keyboardHeight = (notification.userInfo![UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
   print(keyboardHeight)
}