Xamarin.Forms - HttpClient SendAsync中未处理的异常

Question

I'm facing an exception when trying to send a HTTP request on Android. On WinPhone, it works. This is my code:

        string resp = null;

        using (var client = new HttpClient())
        {
            var httpRequest = new HttpRequestMessage(new HttpMethod("POST"), _uri);
            //client.BaseAddress = new Uri(_uri);
            try
            {
                client.Timeout = TimeSpan.FromSeconds(30);
                var _cancelTokenSource = new CancellationTokenSource();
                var _cancelToken = _cancelTokenSource.Token;
                var response = await client.SendAsync(httpRequest, _cancelToken);
                resp = await response.Content.ReadAsStringAsync();
                //var result = await client.PostAsync("", new StringContent(json.ToString(), Encoding.UTF8, "application/json"));
                //resp = await result.Content.ReadAsStringAsync();
            }
            catch (Exception e)
            {
                Debug.WriteLine("HTTP ERROR: " + e.Message);
                throw e;
            }
        }

On Properties > Android Manifest I've checked INTERNET for permission. Additionally, it goes through an unhandled exception and I cannot see what happed. It didn't show the exactly error, neither arriver on my method for unhandled exception that I've set like this:

AndroidEnvironment.UnhandledExceptionRaiser += AppDroid_UnhandledExceptionHandler;

Any idea about what is wrong or any idea about how to see the error message? On WinPhone it arrive on my method when some unexpected error occurs, then it's easy to fix.

Thanks!

Answer 1

There's a known bug on Android HttpClient. See this: http://forums.xamarin.com/discussion/36470/httpclient-postasync-deadlock-system-net-sockets-connect-internal

Change it to:

using (var client = new HttpClient())
        {
            var httpRequest = new HttpRequestMessage(new HttpMethod("POST"), _uri);
            //client.BaseAddress = new Uri(_uri);
            try
            {
                client.Timeout = TimeSpan.FromSeconds(30);
                var _cancelTokenSource = new CancellationTokenSource();
                var _cancelToken = _cancelTokenSource.Token;
                var response = await client.SendAsync(httpRequest, _cancelToken).ConfigureAwait(false);
                resp = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
            }
            catch (Exception e)
            {
                Debug.WriteLine("HTTP ERROR: " + e.Message);
                throw e;
            }
        }

You could also try ModernHttpClient. It's a direct replacement.