         return $0
     }(UIView(frame: .zero))
     lazy fileprivate var underlineView: UIView = {
-        return UIView(frame: .zero)
+        return GradientUnderlineView(frame: .zero)
     }()
     lazy fileprivate var roundRectView: UIView = {
         $0.isUserInteractionEnabled = true

        } else {
            screenWidth = UIScreen.main.bounds.width
        }
//        return menuItemViews[currentPage].frame.midX - screenWidth / 2
        return menuItemViews[currentPage].frame.origin.x - 10.0
    }
    fileprivate var contentOffsetXForCurrentPage: CGFloat {
        guard menuItemCount > MinimumSupportedViewCount else { return 0.0 }

            if let underlineView = underlineView as? GradientUnderlineView {
                underlineView.startColor = startColor
                underlineView.endColor = endColor
                underlineView.backgroundColor = nil
            } else {
                underlineView.backgroundColor = startColor
            }
