HttpClient非常慢-Xamarin Forms

Question

I'm trying to download some json from a url. I'm debugging the app through my Samsung device, but for some reason, httpclient takes very long to download the data.

When I set the timeout using TimeSpan.FromMinutes(30), httpclient takes very long which is not practicable. When I remove the timeout, however, I get TaskCancelled exception which the try catch block catches.

Has anyone seen this behavior before?

Tried checking the permissions: The only permission the app needs is the internet which by default is granted in the debug mode.

Any help would be appreciated. Thanks!

---

Edit

This is the class responsible for downloading the data:

 public static class DataSource
    {
        public async static void LoadFrom()
        {
               var uri = new Uri("https://api.coinmarketcap.com/v2/ticker/?convert=usd&sort=price");    
            try
            {
                bool isConnected = CrossConnectivity.Current.IsConnected;
                HttpClient myClient = new HttpClient(new Xamarin.Android.Net.AndroidClientHandler());
                var response = await myClient.GetAsync(uri);
                if (response.IsSuccessStatusCode)
                {
                    var Data = await response.Content.ReadAsStringAsync();
                    var CoinMarketCapObject = JsonConvert.DeserializeObject<CoinMarketCap.CoinMarketCapCurrencyData>(Data);
                    List<Currency> currencies = new List<Currency>();
                    if (CoinMarketCapObject != null)
                    {
                        foreach (var Datum in CoinMarketCapObject.Data)
                        {
                            currencies.Add(new Currency(Datum.Value.name, Datum.Value.symbol, Datum.Value.quotes.USD.price));
                        }
                    }
                }
            }
            catch (TimeoutException ex)
            {
                // Check ex.CancellationToken.IsCancellationRequested here.
                // If false, it's pretty safe to assume it was a timeout.
            }
            catch (TaskCanceledException ex)
            {
                // Check ex.CancellationToken.IsCancellationRequested here.
                // If false, it's pretty safe to assume it was a timeout.
            }
            catch (Exception e)
            {
                Debug.Print(e.Message);

            }
        }

    }

I'm calling the LoadFrom method from the OnStart Method.

protected override void OnStart ()
        {
            // Handle when your app starts
            API.DataSource.LoadFrom();
        }

Answer 1

Tested on Huawei P9 Lite ==> few seconds to get the result...

public async void LoadFrom()
{
    var uri = new Uri("https://api.coinmarketcap.com/v2/ticker/?convert=usd&sort=price");
    try
    {
        HttpClient myClient = new HttpClient();
        var response = await myClient.GetStringAsync(uri);
        Console.WriteLine(response);
    }
    catch (TimeoutException ex)
    {
        // Check ex.CancellationToken.IsCancellationRequested here.
        // If false, it's pretty safe to assume it was a timeout.
    }
    catch (TaskCanceledException ex)
    {
        // Check ex.CancellationToken.IsCancellationRequested here.
        // If false, it's pretty safe to assume it was a timeout.
    }
    catch (Exception e)
    {

    }
}

Perhaps your myclient has some issues.. or maybe a network problem

Answer 2

I suspect you are using the HttpClientHandler . The current recommendation from Xamarin is to use the AndroidNativeHandler . This uses the native Android networking stack and has encryption support instead of being virtualised within the .NET runtime. However, the trade-offs are support is only from Android 5 onwards, and some HttpClient features/options are not available.

https://docs.microsoft.com/en-us/xamarin/android/app-fundamentals/http-stack