swift -> a旋钮(UIButton)长按的 实现

给按钮 绑定 长按事件 

        let btnDelete:UIButton = bomBtn();
        btnDelete.setImage(#imageLiteral(resourceName: "delete"), for: .normal);
        //绑定长按
        let longPress = UILongPressGestureRecognizer(target: self, action: #selector(KeyboardViewController.delLongPress(_:)))
        longPress.minimumPressDuration = 0.5;//设置长按时间，默认0.5秒
        longPress.numberOfTouchesRequired = 1;//点按的手指数
        longPress.allowableMovement = 15;//允许多少像素内的活动
        btnDelete.addGestureRecognizer(longPress)

    func delLongPress(_ gestureRecognizer: UIGestureRecognizer) {
 
        if gestureRecognizer.state == UIGestureRecognizerState.began{//保障只在按下的时候才执行
            self.proxy.deleteBackward()
        }

    }