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
![这里写图片描述]()
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：
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1.HttpWebRquest、HttpWebResponse
命名空间: System.Net；程序集: System（位于 System.dll）
1 public class HttpWebRequestUtil
2 {
3 //发送get请求获取bytes
4 public static async System.Threading.Tasks.Task<byte[]> GetBytes(string path)
5 {
6 try
7 {
8 HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(path);
9 request.Method = "get";
10 request.Timeout = 500;
11 //request.Proxy设置代理
12 //path 中可添加querystring参数
13 //request.UserAgent 请求的代理
14 HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
15 if (response.StatusCode == HttpStatusCode.OK)
16 {
17 Stream responseStream = response.GetResponseStream();
18 //将流转成字节
19 byte[] bytes = StreamUtil.StreamToBytes(responseStream);
20 return bytes;
21 }
22 else
23 return null;
24 }
25 catch (Exception ex)
26 {
27 return null;
28 }
29 }
30
31 public static async System.Threading.Tasks.Task<bool> PostForm(string path, string name, string pwd)
32 {
33 try
34 {
35 string formData = "name=" + name +"&pwd=" +pwd ;
36 byte[] bytes = Encoding.UTF8.GetBytes(formData);
37 StringBuilder strBuilder = new StringBuilder();
38 HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(path);
39 request.Method = "get";
40 request.Timeout = 500;
41 request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
42 request.ContentLength = bytes.Length;
43 request.Method = "Post";
44 Stream requestStream = request.GetRequestStream();
45 requestStream.Write(bytes, 0, bytes.Length);
46 requestStream.Close();
47
48 HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
49 if (response.StatusCode == HttpStatusCode.OK)
50 {
51 StreamReader streamReader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
52 string content = JsonConvert.DeserializeObject<string>(streamReader.ReadToEnd());
53 streamReader.Close();
54 if (content == "success")
55 {
56 return true;
57 }
58 else
59 return false;
60 }
61 return false;
62 }
63 catch (Exception ex)
64 {
65 return false;
66 }
67 }
68 }
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/
stackoverflow上restsharp的相关问题汇总： https://stackoverflow.com/questions/tagged/RestSharp
restsharp有一下这么几个重要的有点：
- 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）
- 支持异步操作、支持http的get、post、put、delete等操作
- 使用简单、易调试、request和response的类型齐全
- 功能齐全，支持oAuth 1, oAuth 2, Basic等授权验证、可上传文件
- 自定义序列化和反序列化、自动检测返回的内容类型
1 public class RestSharpUtil
2 {
3 internal static RestClient Instance(string url)
4 {
5 var restClient = new RestClient(url)
6 {
7 Timeout = 5000,
8 ReadWriteTimeout = 5000
9 };
10 return restClient;
11 }
12 public static async System.Threading.Tasks.Task<bool> Post(string url, User user)
13 {
14 RestClient restClient = Instance(url);
15 RestRequest request = new RestRequest();
16 //request.AddQueryParameter("id","") 添加url的参数(AddUrlSegment)
17 //request.AddHeader("Authorization","token");添加请求头参数
18 // request.AddHeader("content-type", "application/x-www-form-urlencoded; charset=UTF-8");
19 request.AddJsonBody(user);
20 //request.AddParameter("application/x-www-form-urlencoded; charset=UTF-8", user, ParameterType.RequestBody);
21 var response = await restClient.ExecutePostTaskAsync(request);
22 //var response = await restClient.ExecutePostTaskAsync<string>(request); 自动序列化
23 if (response.StatusCode == System.Net.HttpStatusCode.OK)
24 {
25 var result = JsonConvert.DeserializeObject<string>(response.Content);
26 if (result == "success")
27 {
28 return true;
29 }
30 return false;
31 }
32 else
33 {
34 return false;
35 }
36 }
37 public static async System.Threading.Tasks.Task<byte[]> Get(string url)
38 {
39 RestClient restClient = Instance(url);
40 RestRequest request = new RestRequest();
41 var response = await restClient.ExecuteGetTaskAsync(request);
42 if (response.StatusCode == System.Net.HttpStatusCode.OK)
43 {
44 var bytes = response.RawBytes;
45 return bytes;
46 }
47 return null;
48 }
49 }
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。
1 /// <summary>
2 /// Serializes obj to format specified by RequestFormat, but passes xmlNamespace if using the default XmlSerializer
3 /// The default format is XML. Change RequestFormat if you wish to use a different serialization format.
4 /// </summary>
5 /// <param name="obj">The object to serialize</param>
6 /// <param name="xmlNamespace">The XML namespace to use when serializing</param>
7 /// <returns>This request</returns>
8 public IRestRequest AddBody(object obj, string xmlNamespace)
9 {
10 string serialized;
11 string contentType;
12
13 // TODO: Make it possible to change the serialiser
14 switch (RequestFormat)
15 {
16 case DataFormat.Json:
17 serialized = JsonSerializer.Serialize(obj);
18 contentType = JsonSerializer.ContentType;
19 break;
20
21 case DataFormat.Xml:
22 XmlSerializer.Namespace = xmlNamespace;
23 serialized = XmlSerializer.Serialize(obj);
24 contentType = XmlSerializer.ContentType;
25 break;
26
27 default:
28 serialized = "";
29 contentType = "";
30 break;
31 }
32
33 // passing the content type as the parameter name because there can only be
34 // one parameter with ParameterType.RequestBody so name isn't used otherwise
35 // it's a hack, but it works :)
36 return AddParameter(contentType, serialized, ParameterType.RequestBody);
37 }
38
39 /// <summary>
40 /// Serializes obj to data format specified by RequestFormat and adds it to the request body.
41 /// The default format is XML. Change RequestFormat if you wish to use a different serialization format.
42 /// </summary>
43 /// <param name="obj">The object to serialize</param>
44 /// <returns>This request</returns>
45 public IRestRequest AddBody(object obj)
46 {
47 return AddBody(obj, "");
48 }
49
50 /// <summary>
51 /// Serializes obj to JSON format and adds it to the request body.
52 /// </summary>
53 /// <param name="obj">The object to serialize</param>
54 /// <returns>This request</returns>
55 public IRestRequest AddJsonBody(object obj)
56 {
57 RequestFormat = DataFormat.Json;
58
59 return AddBody(obj, "");
60 }
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
1 public class HttpClientUtil
2 {
3 public static async System.Threading.Tasks.Task<byte[]> GetBytes(string path)
4 {
5 HttpClient client = new HttpClient();
6 try
7 {
8 HttpResponseMessage response = await client.GetAsync(path);
9 if (response.StatusCode == System.Net.HttpStatusCode.OK)
10 {
11 byte[] bytes = await response.Content.ReadAsByteArrayAsync();
12 return bytes;
13 }
14 return null;
15 }
16 catch (Exception ex)
17 {
18 return null;
19 }
20 finally
21 {
22 client.Dispose();
23 }
24 }
25
26 public static async System.Threading.Tasks.Task<bool> PostForm(string path, Dictionary<string,string> _params)
27 {
28
29 var handler = new HttpClientHandler() { AutomaticDecompression = System.Net.DecompressionMethods.GZip };
30 HttpClient client = new HttpClient();
31 try
32 {
33 client.Timeout = TimeSpan.FromSeconds(5);
34 //HttpContent httpContent = new StringContent(postData);
35 //httpContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/x-www-form-urlencoded");
36 HttpContent httpContent = new FormUrlEncodedContent(_params);
37 var response = await client.PostAsync(path, httpContent);
38 if (response.StatusCode == System.Net.HttpStatusCode.OK)
39 {
40 string result = await response.Content.ReadAsStringAsync();
41 result = JsonConvert.DeserializeObject<string>(result);
42 if (result == "success")
43 return true;
44 return false;
45 }
46 return false;
47 }
48 catch (Exception ex)
49 {
50 return false;
51 }
52 finally
53 {
54 client.Dispose();
55 }
56 }
57 }
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
- HttpURLConnection conn = (HttpURLConnection)url.OpenConnection();创建一个URL对象
- conn.ConnectTimeout = 5000; conn.RequestMethod = “get”;设置请求方式和连接超时的时间
- inputStream = conn.InputStream;获取服务器返回的输入流
- 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 = 5000;
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 = 5000;
conn.ConnectTimeout = 5000;
//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), 0, 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[64 * 1024];
int i;
try
{
while ((i = stream.Read(buffer, 0, buffer.Length)) > 0)
{
memoryStream.Write(buffer, 0, 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(5, TimeUnit.Seconds)//连接超时5秒
.WriteTimeout(5, TimeUnit.Seconds)//写入数据超时5秒
.ReadTimeout(5, 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() == 200)
{
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() == 200)
{
var stream = response.Body().ByteStream();
var bytes = StreamUtil.StreamToBytes(stream);
return bytes;
}
return null;
}
}
