Swift 3 点击屏幕任意位置隐藏键盘

func hideKeyboardWhenTappedAround() {
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self,action: #selector(UIViewController.dismissKeyboard))
        tap.cancelstouchesInView = false
        view.addGestureRecognizer(tap)
    }