public static let UIKeyboardWillShow: NSNotification.Name

    public static let UIKeyboardDidShow: NSNotification.Name

    public static let UIKeyboardWillHide: NSNotification.Name

    public static let UIKeyboardDidHide: NSNotification.Name

//键盘弹起

    @objc private func willShow(nottification:NSNotification){

        let info:NSDictionary = nottification.userInfo as NSDictionary!

//        print(info)

       //通过输出看到下面的信息

         /*

Optional([AnyHashable("UIKeyboardCenterBeginUserInfoKey"): NSPoint: {207, 849},

AnyHashable("UIKeyboardIsLocalUserInfoKey"): 1,

AnyHashable("UIKeyboardCenterEndUserInfoKey"): NSPoint: {207, 623},

AnyHashable("UIKeyboardBoundsUserInfoKey"): NSRect: {{0, 0}, {414, 226}},

AnyHashable("UIKeyboardFrameEndUserInfoKey"): NSRect: {{0, 510}, {414, 226}},

AnyHashable("UIKeyboardAnimationCurveUserInfoKey"): 7,

AnyHashable("UIKeyboardFrameBeginUserInfoKey"): NSRect: {{0, 736}, {414, 226}},

            
AnyHashable("UIKeyboardAnimationDurationUserInfoKey"): 0.25])

 */

        //取出键盘的高度

        let keyValue = info.object(forKey: "UIKeyboardFrameEndUserInfoKey")

        let keyRect = (keyValue as AnyObject).cgRectValue

        let height = keyRect?.size.height

        print(height!)

    }

    //键盘收起

    @objc private func willHide(nottification:NSNotification){

    }