xamarin android网络请求总结

xamarin android中网络请求的框架非常多，在项目中使用的是第三方的一个网络请求框架restsharp，应该是github上.net网络请求最多star的框架，没有之一。这里就简单汇总了其他的一些网络请求的例子，主要还是分为android和.net两种平台。.net 中可以使用HttpWebRequest、HttpClient、RestSharp第三框的一些框架，android的有HttpURLConnectin、HttpClient、OkHttp、Retrofit、Volley

下面就用.net中的httpwebrequest、httpclient、restsharp和android中的httpURLConnection、okhttp实现一个get方式获取图片、post方式提交表单，适合新手入门看看总结一下。 
效果图如下： 

1.HttpWebRquest、HttpWebResponse

命名空间: System.Net；程序集: System（位于 System.dll）

   public class HttpWebRequestUtil
     {
         //发送get请求获取bytes
         public static async System.Threading.Tasks.Task<byte[]> GetBytes(string path)
         {
             try
             {
                 HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(path);
                 request.Method = "get";
                 request.Timeout = ;
                 //request.Proxy设置代理
                 //path 中可添加querystring参数
                 //request.UserAgent 请求的代理
                 HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
                 if (response.StatusCode == HttpStatusCode.OK)
                 {
                     Stream responseStream = response.GetResponseStream();
                     //将流转成字节
                     byte[] bytes = StreamUtil.StreamToBytes(responseStream);
                     return bytes;
                 }
                 else
                     return null;
             }
             catch (Exception ex)
             {
                 return null;
             }
         }

         public static async System.Threading.Tasks.Task<bool> PostForm(string path, string name, string pwd)
         {
             try
             {
                 string formData = "name=" + name +"&pwd=" +pwd ;
                 byte[] bytes = Encoding.UTF8.GetBytes(formData);
                 StringBuilder strBuilder = new StringBuilder();
                 HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(path);
                 request.Method = "get";
                 request.Timeout = ;
                 request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
                 request.ContentLength = bytes.Length;
                 request.Method = "Post";
                 Stream requestStream = request.GetRequestStream();
                 requestStream.Write(bytes, ,  bytes.Length);
                 requestStream.Close();

                 HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
                 if (response.StatusCode == HttpStatusCode.OK)
                 {
                     StreamReader streamReader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                     string content = JsonConvert.DeserializeObject<string>(streamReader.ReadToEnd());
                     streamReader.Close();
                     if (content == "success")
                     {
                         return true;
                     }
                     else
                         return false;
                 }
                 return false;
             }
             catch (Exception ex)
             {
                 return false;
             }
         }
     }

2.RestSharp .net常用的http网络请求库

当然重点还是说一下这个的。restsharp在github上的star应该是.net网络请求库最多的，（和第二名的差距比较大）。可以在nuget上直接添加引用restsharp。 
github地址：https://github.com/restsharp/RestSharp 
restSharp官网：http://restsharp.org/ 
*上restsharp的相关问题汇总： https://*.com/questions/tagged/RestSharp 
restsharp有一下这么几个重要的有点：

1. 轻量级的、基于HttpWebRequest的封装（不依赖任何第三方组件、支持.net 任何平台上）
2. 支持异步操作、支持http的get、post、put、delete等操作
3. 使用简单、易调试、request和response的类型齐全
4. 功能齐全，支持oAuth 1, oAuth 2, Basic等授权验证、可上传文件
5. 自定义序列化和反序列化、自动检测返回的内容类型

     public class RestSharpUtil
     {
         internal static RestClient Instance(string url)
         {
             var restClient = new RestClient(url)
             {
                 Timeout = ,
                 ReadWriteTimeout =
             };
             return  restClient;
         }
         public static async System.Threading.Tasks.Task<bool> Post(string url, User user)
         {
             RestClient restClient = Instance(url);
             RestRequest request = new RestRequest();
             //request.AddQueryParameter("id","")  添加url的参数(AddUrlSegment)
             //request.AddHeader("Authorization","token");添加请求头参数
             // request.AddHeader("content-type", "application/x-www-form-urlencoded; charset=UTF-8");
             request.AddJsonBody(user);
             //request.AddParameter("application/x-www-form-urlencoded; charset=UTF-8", user, ParameterType.RequestBody);
             var response = await restClient.ExecutePostTaskAsync(request);
             //var response = await restClient.ExecutePostTaskAsync<string>(request); 自动序列化
             if (response.StatusCode == System.Net.HttpStatusCode.OK)
             {
                 var result = JsonConvert.DeserializeObject<string>(response.Content);
                 if (result == "success")
                 {
                     return true;
                 }
                 return false;
             }
             else
             {
                 return false;
             }
         }
         public static async System.Threading.Tasks.Task<byte[]> Get(string url)
         {
             RestClient restClient = Instance(url);
             RestRequest request = new RestRequest();
             var response = await restClient.ExecuteGetTaskAsync(request);
             if (response.StatusCode == System.Net.HttpStatusCode.OK)
             {
                 var bytes = response.RawBytes;
                 return  bytes;
             }
             return null;
         }
     }

post请求和get请求在编码类型不同，get：仅一种 application/x-www-form-urlencoded，post：application/x-www-form-urlencoded 或 multipart/form-data……等多种编码方式。 

restsharp在发送post请求方式时必须设置header的content-type解码方式。 
request.AddJsonBody(user);等同于： 
request.AddParameter(“application/x-www-form-urlencoded; charset=UTF-8”, user, ParameterType.RequestBody);等同于： 
request.RequestFormat =DataFormat.Json; 
request.AddBody(user); 
这里备注一下以前犯的一个错误，用了AddBody方法必须添加 request.RequestFormat =DataFormat.Json; ，不然会出异常 
我们看看下面的AddBody的源码可以知道，除restsharp，.net第三方的网络请求框架还有flurl.http。

   /// <summary>
         ///     Serializes obj to format specified by RequestFormat, but passes xmlNamespace if using the default XmlSerializer
         ///     The default format is XML. Change RequestFormat if you wish to use a different serialization format.
         /// </summary>
         /// <param name="obj">The object to serialize</param>
         /// <param name="xmlNamespace">The XML namespace to use when serializing</param>
         /// <returns>This request</returns>
         public IRestRequest AddBody(object obj, string xmlNamespace)
         {
             string serialized;
             string contentType;

             // TODO: Make it possible to change the serialiser
             switch (RequestFormat)
             {
                 case DataFormat.Json:
                     serialized = JsonSerializer.Serialize(obj);
                     contentType = JsonSerializer.ContentType;
                     break;

                 case DataFormat.Xml:
                     XmlSerializer.Namespace = xmlNamespace;
                     serialized = XmlSerializer.Serialize(obj);
                     contentType = XmlSerializer.ContentType;
                     break;

                 default:
                     serialized = "";
                     contentType = "";
                     break;
             }

             // passing the content type as the parameter name because there can only be
             // one parameter with ParameterType.RequestBody so name isn't used otherwise
             // it's a hack, but it works :)
             return AddParameter(contentType, serialized, ParameterType.RequestBody);
         }

         /// <summary>
         ///     Serializes obj to data format specified by RequestFormat and adds it to the request body.
         ///     The default format is XML. Change RequestFormat if you wish to use a different serialization format.
         /// </summary>
         /// <param name="obj">The object to serialize</param>
         /// <returns>This request</returns>
         public IRestRequest AddBody(object obj)
         {
             return AddBody(obj, "");
         }

         /// <summary>
         ///     Serializes obj to JSON format and adds it to the request body.
         /// </summary>
         /// <param name="obj">The object to serialize</param>
         /// <returns>This request</returns>
         public IRestRequest AddJsonBody(object obj)
         {
             RequestFormat = DataFormat.Json;

             return AddBody(obj, "");
         }

3.HttpClient

性能上不如httpwebrequest，用的非常少，据说使用的时候要注意不少，这里只是写一个简单的例子，不喜勿喷。 
需要添加引用System.Http.Http

   public class HttpClientUtil
     {
         public static async System.Threading.Tasks.Task<byte[]> GetBytes(string path)
         {
             HttpClient client = new HttpClient();
             try
             {
                 HttpResponseMessage response = await client.GetAsync(path);
                 if (response.StatusCode == System.Net.HttpStatusCode.OK)
                 {
                     byte[] bytes = await response.Content.ReadAsByteArrayAsync();
                     return bytes;
                 }
                 return null;
             }
             catch (Exception ex)
             {
                 return null;
             }
             finally
             {
                 client.Dispose();
             }
         }

         public static async System.Threading.Tasks.Task<bool> PostForm(string path, Dictionary<string,string> _params)
         {

                 var handler = new HttpClientHandler() { AutomaticDecompression = System.Net.DecompressionMethods.GZip };
                 HttpClient client = new HttpClient();
             try
             {
                 client.Timeout = TimeSpan.FromSeconds();
                 //HttpContent httpContent = new StringContent(postData);
                 //httpContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/x-www-form-urlencoded");
                 HttpContent httpContent = new FormUrlEncodedContent(_params);
                 var response = await client.PostAsync(path, httpContent);
                 if (response.StatusCode == System.Net.HttpStatusCode.OK)
                 {
                     string result = await response.Content.ReadAsStringAsync();
                     result = JsonConvert.DeserializeObject<string>(result);
                     if (result == "success")
                         return true;
                     return false;
                 }
                 return false;
             }
             catch (Exception ex)
             {
                 return false;
             }
             finally
             {
                 client.Dispose();
             }
         }
     }

上面介绍了三种.net方面的网络请求的方法，下面就来说说android方面的网络请求HttpUrlConnection、第三方okhttp。

4.HttpURLConnection

httpURLConnection和HttpWebRequest很相似，是java平台上的一种多用途、轻量级的http客户端，提供的api都非常简单，这一点也是好处，可以使得我们非常方便去拓展他。下面我们简单看下如何使用HttpURLConnection。 
引用来自：Java.Net

1. HttpURLConnection conn = (HttpURLConnection)url.OpenConnection();创建一个URL对象
2. conn.ConnectTimeout = 5000; conn.RequestMethod = “get”;设置请求方式和连接超时的时间
3. inputStream = conn.InputStream;获取服务器返回的输入流
4. conn.Disconnect();最后调用disconnect方法将http连接关掉

    public class HttpUrlConnecUtil
    {
        /// <summary>
        /// get方式获取byte 数组
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public static byte[] getImage(string path)
        {
            URL url = new URL(path);
            HttpURLConnection conn = (HttpURLConnection)url.OpenConnection();
            conn.ConnectTimeout = ;
            conn.RequestMethod = "GET";//小写会报错
            System.IO.Stream inputStream=null;
            try
            {
                if (conn.ResponseCode == HttpStatus.Ok)
                {
                    inputStream = conn.InputStream;
                    return StreamUtil.StreamToBytes(inputStream);
                }
                return null;
            }
            catch (Exception ex)
            {
                return null;
            }
            finally
            {
                inputStream.Close();
                conn.Disconnect();
            }
        }
        public static string post(string  path,string  name,string  pwd)
        {
            string result = string.Empty;
            HttpURLConnection conn = (HttpURLConnection)new URL(path).OpenConnection();
            conn.RequestMethod = "POST";
            conn.ReadTimeout = ;
            conn.ConnectTimeout = ;
            //设置运行输入、输出
            conn.DoOutput =  true;
            conn.DoInput = true;
            //post 方式不能缓存，需要手动设置false
            conn.UseCaches = false;
            string data = "name=" + URLEncoder.Encode(name, "UTF-8") + "&pwd=" + URLEncoder.Encode(pwd,"UTF-8");
            Stream outSteam=null;
            //获取输出流
            try
            {
                outSteam = conn.OutputStream;
                outSteam.Write(Encoding.UTF8.GetBytes(data), , data.Length);
                outSteam.Flush();
                if (conn.ResponseCode == HttpStatus.Ok)
                {
                    Stream input = conn.InputStream;
                    byte[] bytes = StreamUtil.StreamToBytes(input);
                    result = bytes.ToString();
                }
                return result;
            }
            catch (Exception ex)
            {
                return "";
            }
            finally {
                outSteam.Close();
                conn.Disconnect();
            }
        }
    }
            /// <summary>
        /// 将流转成byte数组
        /// </summary>
        /// <param name="stream"></param>
        /// <param name="bytes"></param>
        public static  byte[] StreamToBytes(Stream stream)
        {
            MemoryStream memoryStream = new MemoryStream();
            byte[] buffer = new byte[ * ];
            int i;
            try
            {
                while ((i = stream.Read(buffer, , buffer.Length)) > )
                {
                    memoryStream.Write(buffer, , i);
                }
                var bytes = memoryStream.ToArray();
                return bytes;
            }
            catch (Exception ex)
            {
                return null;
            }
            finally {
                memoryStream.Close();
                stream.Close();
            }
        }

5.OkHttp 最火的android网络请求框架

okhttp是一个第三方的网络请求框架，被广泛适用于android中请求网络数据，是一个一个轻量级的框架，有移动支付Square公司贡献（Picasso和LeakCanary），和HttpURLConnection和api是一致的。在xamarin android中使用的时候需要在nuget中添加引用OkHttp，命名空间：using Square.OkHttp3; 
okhttp官网：http://square.github.io/okhttp/ 
github地址：https://github.com/square/okhttp 
除了okhttp外，android中比较流行的网络请求框架还有 
retrofit，retrofit2依赖于okhttp；github地址：http://square.github.io/retrofit/，拓展性比较强 
volley：google在2013年推出的android异步网络请求框架和图片加载框架 
下面看看，如何在xamarin android中使用okhttp发送get，post请求吧。

 public class OkHttpClientUtil
    {
        private OkHttpClient httpClient;
        public OkHttpClientUtil()
        {
             httpClient = new OkHttpClient.Builder()
            .ConnectTimeout(, TimeUnit.Seconds)//连接超时5秒
            .WriteTimeout(, TimeUnit.Seconds)//写入数据超时5秒
            .ReadTimeout(, TimeUnit.Seconds)//读取数据超时5秒
            .Build();
        }
        public static OkHttpClientUtil Instance()
        {
            return new OkHttpClientUtil();
        }

        public async System.Threading.Tasks.Task<bool> Post(string url, User user)
        {
            FormBody.Builder formBody = new FormBody.Builder(); //创建表单请求体
            formBody.Add("name", user.Name);
            formBody.Add("pwd", user.Pwd);
            Request request = new Request.Builder().AddHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8").Url(url).Post(formBody.Build()).Build();
            var response = await httpClient.NewCall(request).ExecuteAsync();
            if (response.Code() == )
            {
                var  result =JsonConvert.DeserializeObject<string>(response.Body().String());
                if (result == "success")
                {
                    return true;
                }
                return false;
            }
            return false;
        }

        public  async System.Threading.Tasks.Task<byte[]> Get(string url)
        {
            Request request = new Request.Builder().Url(url).Build();
            Response response = await httpClient.NewCall(request).ExecuteAsync();
            if (response.Code() == )
            {
                var stream = response.Body().ByteStream();
                var bytes = StreamUtil.StreamToBytes(stream);
                return bytes;
            }
            return null;
        }
    }

有兴趣关注一下我的个人公众号，专注dotNet开发，谢谢