Unity webview loading webpage locally/by storing cache

I am trying to build a unity project, in my project i have to show the web page in app using unity webview either by loading locally or by once storing cache of that web page. i have tried loading locally by downloading a web page but without internet the content of the html files loaded but CSS, JS and Images are not. for loading locally i have pasted the folders and HTML file to a folder in project-> Assests-> Streaming Assets. Image for folders and HTML file is Streaming Assets directory Image the underlined folders and file is used. And in unity editor link for the file is provided like this:- Unity Editor Image and script used to load the file is below

 case RuntimePlatform.OSXEditor:
     case RuntimePlatform.OSXPlayer:
     case RuntimePlatform.IPhonePlayer:
     case RuntimePlatform.Android:
         if (Url.StartsWith("http")) {
             webViewObject.LoadURL(Url.Replace(" ", "%20"));
         } else {
             webViewObject.LoadURL("StreamingAssets/" + Url.Replace(" ", "%20"));
             var src = System.IO.Path.Combine(Application.streamingAssetsPath, Url);
             var dst = System.IO.Path.Combine(Application.persistentDataPath, Url);
             var result = "";
             if (src.Contains("://")) {
                 var www = new WWW(src);
                 yield return www;
                 result = www.text;
             } else {
                 result = System.IO.File.ReadAllText(src);
             }
             System.IO.File.WriteAllText(dst, result);
             webViewObject.LoadURL("file://" + dst.Replace(" ", "%20"));
         }
         if (Application.platform != RuntimePlatform.Android) {
             webViewObject.EvaluateJS(
                 "window.addEventListener('load', function() {" +
                 "    window.Unity = {" +
                 "        call:function(msg) {" +
                 "            var iframe = document.createElement('IFRAME');" +
                 "            iframe.setAttribute('src', 'unity:' + msg);" +
                 "            document.documentElement.appendChild(iframe);" +
                 "            iframe.parentNode.removeChild(iframe);" +
                 "            iframe = null;" +
                 "        }" +
                 "    }" +
                 "}, false);");
         }
         break;
     #else

If anyone Knows Please help.