ios开发wkwebview禁用系统长按保存图片菜单

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        // 禁用系统自动的长按图片菜单
        self.webview.evaluateJavaScript("document.documentElement.style.webkitTouchCallout='none';", completionHandler: nil)
    }