Question

我无法使用Xamarin表单中的PLC项目从Web服务检索数据。我已经尝试了WebRequest和HttpClient，但得到了各种异常。我也试过了运行此示例中的代码：

ConnectFailure（网络无法访问）

HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create ("http://localhost:3000/profile/contacts");
        webRequest.UseDefaultCredentials = true;
        webRequest.Method = "GET";
        webRequest.Accept = "application/json";
        webRequest.ContentType = "application/json";
        webRequest.BeginGetResponse ((ar) => {
            var request = (HttpWebRequest)ar.AsyncState;
            try {
                using (var response = (HttpWebResponse)request.EndGetResponse (ar)) {                              
                    var s = response.GetResponseStream ();
                }
            } catch (Exception ex) {
                var xy = ex;
            }

        }, webRequest);

ConnectFailure（请求的地址在此上下文中无效）

            var client = new System.Net.Http.HttpClient ();
            client.BaseAddress = new Uri("http://localhost:3000/");
            client.DefaultRequestHeaders.Clear ();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            var response = await client.GetStringAsync ("profile/contacts");

我还尝试运行此示例中的代码：https://github.com/conceptdev/xamarin-forms-samples/tree/master/HttpClient/HttpClientDemo 在尝试发出请求时会抛出namesresolutionfail异常。

var client = new System.Net.Http.HttpClient ();
                client.BaseAddress = new Uri("http://api.geonames.org/");
                var response = await client.GetAsync("earthquakesJSON?north=44.1&south=-9.9&east=-22.4&west=55.2&username=bertt");
                var earthquakesJson = response.Content.ReadAsStringAsync().Result;
                var rootobject = JsonConvert.DeserializeObject<Rootobject>(earthquakesJson);
                return rootobject.earthquakes;

我已经测试了我的其余api（用Node.Js编写）并且它按预期返回数据。

Answer 1

Eee，Android的localhost是什么？它不知道localhost实际上是你的计算机。根据api.geonames.org，这可能是一个模拟器问题。你在哪里测试你的应用程序？试试真实的设备。

Xamarin Forms的问题从webservices / rest api检索json

1 个答案: