Ios WKWebView发布请求Swift 5

我正在尝试使用下面的代码在WKWebview中打开带有一些post参数的URL

    //let postdata = strPostString.data(using: .utf8)
    var request = URLRequest(url: URL(string:posturl)!)
    request.httpMethod = "POST"
    let bodyData = "data1=\(String(describing: strPostString))"
    request.httpBody = bodyData.data(using: .utf8)!
    request.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
    jioPGWebV.navigationDelegate  = self
    jioPGWebV.load(request)

但无法加载页面

始终在委托方法中获取nil httpbody

  func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    print(navigationAction.request.httpBody)
    decisionHandler(.allow)
}

请帮忙