Xamarin 本机共享项目 HttpClient 不起作用

Question

我创建了支持 Android 和 iOS 移动平台的 Xamrin 原生共享项目。我想在这两个移动应用程序中使用 REST 服务。如果我使用 HttpClient 向 REST API 发出请求，则它不起作用。给我的回应是：

{StatusCode：404，ReasonPhrase：“未找到”，版本：1.1，内容： System.Net.Http.StreamContent，标头：{ 变化：接受编码 服务器：DPS/1.0.3 X-SiteId：1000 Set-Cookie：dps_site_id=1000；路径=/ 日期：2016 年 7 月 27 日，星期三，格林威治标准时间 12:09:00 连接：保持活动 内容类型：文本/html； charset=utf-8 内容长度：964 }} 内容：{System.Net.Http.StreamContent} 标头：{变化： 接受编码服务器：DPS/1.0.3 X-SiteId：1000 Set-Cookie： dps_site_id=1000；路径=/ 日期：格林威治标准时间 2016 年 7 月 27 日星期三 12:09:00 连接：保持活动 } IsSuccessStatusCode：false ReasonPhrase： “未找到”状态码：System.Net.HttpStatusCode.NotFound 版本： {1.1} 非公共成员：

如果我使用 HttpWebResponse 发出请求，它会成功获取数据。

你能告诉我为什么 HttpClient 不工作吗？

    // Using HttpClient
    public async Task<string> GetCategories11(string token)
    {
        using (HttpClient client = new HttpClient())
        {
            var url = string.Format("{0}{1}", BaseUrl, CategoriesEndPoint);
            var uri = new Uri(url);
            client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
            client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
            try
            {
                using (var response = await client.GetAsync(uri))
                {
                    if (response.IsSuccessStatusCode)
                    {
                        var contentStr = await response.Content.ReadAsStringAsync();
                        return contentStr;
                    }
                    else
                        return null;
                }
            }
            catch
            {
                return null;
            }
        }
    }

    // Using HttpWebRequest
    public async Task<ResponseModel> GetCategories(string token)
    {
        // Create an HTTP web request using the URL:
        var url = string.Format("{0}{1}", RequestClient.BaseUrl, CategoriesEndPoint);
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
        request.ContentType = "application/json";
        request.Headers.Add("Authorization", "Bearer " + token);
        request.Accept = "application/json";
        request.Method = "GET";

        try
        {
            // Send the request to the server and wait for the response:
            using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())
            {
                // Get a stream representation of the HTTP web response.
                using (Stream stream = response.GetResponseStream())
                {
                    // Use this stream to build a JSON object.
                    JsonValue jsonDoc = await Task.Run(() => JsonObject.Load(stream));

                    return new ResponseModel() { Success = true, ResponseValue = jsonDoc.ToString(), StatusCode = response.StatusCode };
                }
            }
        }
        catch (WebException ex)
        {
            using (var stream = ex.Response.GetResponseStream())
            using (var reader = new StreamReader(stream))
            {
                return new ResponseModel() { ResponseValue = reader.ReadToEnd(), StatusCode = ((HttpWebResponse)ex.Response).StatusCode };
            }
        }
        catch (Exception ex)
        {
            return new ResponseModel() { ResponseValue = ex.Message };
        }
    }

Answer 1

调试并暂停在线using (var response = await client.GetAsync(uri)) uri 是什么？和GetCategories()中的一样吗？

如果您愿意，这是我在 Xamarin.Android 中使用的方法，它适用于不记名令牌。根据您的需要进行更改，您可能不需要执行JsonConvert.DeserializeObject() 部分。

protected async Task<T> GetData<T>(string dataUri, string accessToken = null, string queryString = null)
{
    var url = baseUri + "/" + dataUri + (!string.IsNullOrEmpty(queryString) ? ("?" + queryString) : null);
    try
    {
        using (var httpClient = new HttpClient() { Timeout = new TimeSpan(0, 0, 0, 0, SharedMobileHelper.API_WEB_REQUEST_TIMEOUT) })
        {
            // Set OAuth authentication header
            if (!string.IsNullOrEmpty(accessToken))
                httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

            using (HttpResponseMessage response = await httpClient.GetAsync(url))
            {
                string content = null;
                if (response != null && response.Content != null)
                    content = await response.Content.ReadAsStringAsync();

                if (response.StatusCode == HttpStatusCode.OK ||
                    response.StatusCode == HttpStatusCode.Created)
                {
                    if (content.Length > 0)
                        return JsonConvert.DeserializeObject<T>(content);
                }
                else if (response.StatusCode == HttpStatusCode.InternalServerError)
                {
                    throw new Exception("Internal server error received (" + url + "). " + content);
                }
                else
                {
                    throw new Exception("Bad or invalid request received (" + url + "). " + content);
                }
            }
        }
    }
    catch (Exception ex)
    {
        Log.Error("Could not fetch data via GetData (" + url + ").", ex.ToString());
        throw ex;
    }
    return default(T);
}