WKWebView上未显示JS浮动按钮

Question

JS浮动按钮未在WKWebView上显示，但在模拟器/ iPhone Safari和Chrome浏览器上完美显示。这是我的配置代码，我错过了什么吗？

self.viewWeb.configuration.preferences.javaScriptEnabled = true
    self.viewWeb.configuration.preferences.javaScriptCanOpenWindowsAutomatically = true
    self.viewWeb.scrollView.showsHorizontalScrollIndicator = false
    self.viewWeb.scrollView.bouncesZoom = false
    self.viewWeb.scrollView.isMultipleTouchEnabled = false
    self.viewWeb.scrollView.minimumZoomScale = 1.0
    self.viewWeb.scrollView.maximumZoomScale = 1.0
    self.viewWeb.sizeToFit()
    self.viewWeb.scrollView.bounces = false
    self.viewWeb.customUserAgent = "Mozilla/5.0 (iPhone; CPU iPhone OS 10_3 like Mac OS X) AppleWebKit/603.1.23 (KHTML, like Gecko) Version/10.0 Mobile/14E5239e Safari/602"
    self.viewWeb.allowsBackForwardNavigationGestures = true
    self.viewWeb.isMultipleTouchEnabled = true
    self.viewWeb.evaluateJavaScript("document.documentElement.style.webkitUserSelect='none'", completionHandler: nil)
    self.viewWeb.evaluateJavaScript("document.documentElement.style.webkitTouchCallout='none'", completionHandler: nil)