Downloading info from JSON(Xamarin C#)

Question

I am writing Android app in Xamarin C#.

I parse info from JSON and then show it in fields.

I use this code:

string url2 = "http://papajohn.pp.ua/?mkapi=getProductsByCat&cat_id=74";
        JsonValue json = await FetchAsync(url2);
 private async Task<JsonValue> FetchAsync(string url)
    {
        // Create an HTTP web request using the URL:
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
        request.ContentType = "application/json";
        request.Method = "GET";

        // Send the request to the server and wait for the response:
        using (WebResponse response = await request.GetResponseAsync())
        {
            // Get a stream representation of the HTTP web response:
            using (Stream stream = response.GetResponseStream())
            {
                // Use this stream to build a JSON document object:
                JsonValue jsonDoc = await Task.Run(() => JsonObject.Load(stream));
                //dynamic data = JObject.Parse(jsonDoc[15].ToString);
                Console.Out.WriteLine("Response: {0}", jsonDoc.ToString());


                // Return the JSON document:
                return jsonDoc;
            }
        }
    }

But I have one problem. When I open Activity it freezes for 2-3 seconds and then all info shows in fields.

Can I make that data download smoothly. First field, then second etc.

And if I can, how?

Answer 1

I would recommend implementing the proper usage of async/await in C#, and switching to HttpClient, which also implements the proper usage of async/await. Below is a code sample that will retrieve your Json outside of the UI Thread:

var url2 = "http://papajohn.pp.ua/?mkapi=getProductsByCat&cat_id=74";
var jsonValue = await FetchAsync(url2);

private async Task<JsonValue> FetchAsync(string url)
{
   System.IO.Stream jsonStream;
   JsonValue jsonDoc;

   using(var httpClient = new HttpClient())
   {
     jsonStream = await httpClient.GetStreamAsync(url);
     jsonDoc = JsonObject.Load(jsonStream);
   }

   return jsonDoc;
}

If you're writing your code in an Android project, you'll need to add the System.Net.Http DLL as a reference. If you're writing your code in aPCL, then you'll need to install the Microsoft Http Client Libraries Nuget Package. For even improve performance, I recommend using ModernHttpClient, which can also be installed from Nuget.