WKWebView点击事件和滚动事件

需求1：我们在最下方有一个按钮 网页向上滚动的时候：消失 向下滚动的时候: 出现

  func scrollViewDidScroll(_ scrollView: UIScrollView) {
    newContentOffsetY = scrollView.contentOffset.y

    if (newContentOffsetY > oldContentOffsetY) && (oldContentOffsetY > contentOffsetY) {
      returnView.alpha = 0
      self.rightUpdateBtn?.isHidden = true
    }else if (newContentOffsetY < oldContentOffsetY) && (oldContentOffsetY < contentOffsetY){

      if newContentOffsetY < ScreenHeight*1.5 {
        returnView.alpha = 0

      }else{
        returnView.alpha = 1
      }

      self.rightUpdateBtn?.isHidden = false
    }

    if (scrollView.contentOffset.y + scrollView.height + 15) > scrollView.contentSize.height {
      returnView.alpha = 1
      self.rightUpdateBtn?.isHidden = false
    }

  }

需求2: 控制网页的点击 控制跳转方向

  func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Swift.Void){

    let tmpStr = navigationAction.request.url?.absoluteString
    //    print("点击的事件拦截: \(navigationAction.request.url?.absoluteString)")
    if  (tmpStr?.contains(agodaDownStr ?? "")) ?? false {
      decisionHandler(WKNavigationActionPolicy.cancel)
      SVProgressHUD.show(nil, status: "咱不支持跳转app")
    }else{
      decisionHandler(WKNavigationActionPolicy.allow)
    }

  }