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1.写在前面：

　　网络请求框架层出不穷，像google的volley，xutils等等。听说Okhttp性能很高，最近写新项目，决定用Okhttp来尝试一下（原谅我是小白，第一次使用，以前还是用volley），以此来记录一下自己的心得。

2.首先来介绍一下Okhttp：

　　Okhttp出自鼎鼎大名的Square，官方github地址：https://github.com/square/okhttp；它基本包含所有常用的网络请求，同步、异步的get、post请求，文件上传下载等等，废话不说，直接进入教程

3.Okhttp的使用：

１）首先添加依赖：

Download the latest JAR or grab via Maven:
<dependency><groupId>com.squareup.okhttp3</groupId><artifactId>okhttp</artifactId><version>3.6.0</version>
</dependency>
or Gradle:
compile 'com.squareup.okhttp3:okhttp:3.6.0'

还在用eclipse的童鞋也可以下载jar使用，不过抓紧时间换Android Studio吧；

２）同时别忘了添加添加网络权限：

<uses-permission android:name="android.permission.INTERNET"/>

３）开始编写代码：

http同步get请求：

    /*** 同步的Get请求** @param url* @return responseStr* @throws IOException*/public static String getSync(String url) throws IOException {// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();// 创建一个Requestfinal Request request = new Request.Builder().url(url).build();Call call = okHttpClient.newCall(request);// 返回值为responseResponse response = call.execute();// 将response转化成StringString responseStr = response.body().string();return responseStr;}

　　OKHttp请求成功的返回值为Response ，一般可以通过response.body().string()获取返回的字符串；也可以通过response.body().bytes()获取返回的二进制字节数组；也可以通过response.body().byteStream()获取返回的inputStream。 
　　

http异步get请求：

    /*** 异步的Get请求** @param url url*/public static void getAsyn(String url) {// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();// 创建一个Requestfinal Request request = new Request.Builder().url(url).build();Call call = okHttpClient.newCall(request);// 请求加入调度call.enqueue(new Callback() {// 请求失败的回调@Overridepublic void onFailure(Call call, IOException e) {e.printStackTrace();}// 请求成功的回调@Overridepublic void onResponse(Call call, Response response) throws IOException {// 将response转化成StringString responseStr = response.body().string();}});}

　　同上OKHttp请求成功的返回值为Response ，一般可以通过response.body().string()获取返回的字符串；值得注意的是它的返回值是在子线程中而不是UI线程，想要在UI线程中使用，还需要使用handler等，例如：

    // 请求成功的回调@Overridepublic void onResponse(Call call, Response response) throws IOException {// 将response转化成StringString responseStr = response.body().string();runOnUiThread(new Runnable() {@Overridepublic void run() {Toast.makeText(getApplicationContext(), responseStr,Toast.LENGTH_SHORT).show();}}}

　　这样http的异步get请求就完成了，如果每次请求都写如此多的代码而且返回值还不是在UI线程，那每发送一次请求都很麻烦，看到这，你一定会想到封装，没错，将OKHttp封装成一个工具类，每次使用直接去调用就简单多了，在本文最后我也会提供我自己对OKHttp的简单封装，供大家参考。

http同步post请求：

    /*** 同步的Post请求** @param url    url* @param params params* @return responseStr* @throws IOException*/public static String postSync(String url, Map<String, String> params) throws IOException {// RequestBodyRequestBody requestBody;if (params == null) {params = new HashMap<>();}// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();FormBody.Builder builder = new FormBody.Builder();/*** 在这对添加的参数进行遍历*/for (Map.Entry<String, String> map : params.entrySet()) {String key = map.getKey();String value;/*** 判断值是否是空的*/if (map.getValue() == null) {value = "";} else {value = map.getValue();}/*** 把key和value添加到formBody中*/builder.add(key, value);}requestBody = builder.build();// 创建一个Requestfinal Request request = new Request.Builder().url(url).post(requestBody).build();Call call = okHttpClient.newCall(request);// 返回值为responseResponse response = call.execute();// 将response转化成StringString responseStr = response.body().string();return responseStr;}

　　　大家知道，发送post请求时，参数是包含在请求体中的，所以我们去构造RequestBody，最后完成我们Request的构造。

http异步post请求：

    /*** 异步的Post请求** @param url    url* @param params params* @return responseStr*/public static void postAsyn(String url, Map<String, String> params) {// RequestBodyRequestBody requestBody;if (params == null) {params = new HashMap<>();}// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();FormBody.Builder builder = new FormBody.Builder();/*** 在这对添加的参数进行遍历*/for (Map.Entry<String, String> map : params.entrySet()) {String key = map.getKey();String value;/*** 判断值是否是空的*/if (map.getValue() == null) {value = "";} else {value = map.getValue();}/*** 把key和value添加到formBody中*/builder.add(key, value);}requestBody = builder.build();// 创建一个Requestfinal Request request = new Request.Builder().url(url).post(requestBody).build();Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {// 将response转化成StringString responseStr = response.body().string();}});}

　　以上是基于http的异步post请求，上面的例子添加的请求参数是Map，当然也可以添加其他类型的参数，如：

// post传参（byte）
RequestBody byteBody = RequestBody.create(MediaType.parse("application/octet-stream; charset=utf-8"), mapToBytes(params));mapToBytes(params)方法是将params转化成byte

http的文件上传：

    /*** 基于http的文件上传* 通过addFormDataPart可以添加多个上传的文件*/public void uploadMultiFile() {// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();File file = new File(Environment.getExternalStorageDirectory(), "pic.png");RequestBody fileBody = RequestBody.create(MediaType.parse("application/octet-stream"), file);RequestBody requestBody = new MultipartBody.Builder().setType(MultipartBody.FORM).addFormDataPart("image", "pic.png", fileBody).build();Request request = new Request.Builder().url("填写url地址").post(requestBody).build();Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {}});}

http的文件下载：

    /*** 基于http的下载文件请求** @param downloadUrl 下载地址*/public static void downloadRequest(String downloadUrl) {// 创建OKHttpClient对象OkHttpClient okHttpClient = new OkHttpClient();Request request = new Request.Builder().url(downloadUrl).build();Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {// 下载成功后执行的操作}});}

OKHttp的简单封装使用（NetRequest工具类）：

　　以上是OKHttp常用的请求，其他请求类似，不再重复。下面对OKHttp进行简单的封装，使其使用方便，不必每次都写大量的重复方法，同时直接将返回值Response传递到UI线程，将其封装在OKHttp的工具类中，简化代码，下面直接贴代码：

package com.guifa.okhttpdemo.http;import android.os.Handler;
import android.os.Looper;import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.FormBody;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;/*** Created by GuiFa on 2017/2/3.* 网络请求工具类*/
public class NetRequest {private static NetRequest netRequest;private static OkHttpClient okHttpClient; // OKHttp网络请求private Handler mHandler;private NetRequest() {// 初始化okhttp 创建一个OKHttpClient对象，一个app里最好实例化一个此对象okHttpClient = new OkHttpClient();okHttpClient.newBuilder().connectTimeout(10, TimeUnit.SECONDS).readTimeout(10, TimeUnit.SECONDS).writeTimeout(10, TimeUnit.SECONDS);mHandler = new Handler(Looper.getMainLooper());}/*** 单例模式  获取NetRequest实例** @return netRequest*/private static NetRequest getInstance() {if (netRequest == null) {netRequest = new NetRequest();}return netRequest;}//-------------对外提供的方法Start--------------------------------/*** 建立网络框架，获取网络数据，异步get请求（Form）** @param url      url* @param params   key value* @param callBack data*/public static void getFormRequest(String url, Map<String, String> params, DataCallBack callBack) {getInstance().inner_getFormAsync(url, params, callBack);}/*** 建立网络框架，获取网络数据，异步post请求（Form）** @param url      url* @param params   key value* @param callBack data*/public static void postFormRequest(String url, Map<String, String> params, DataCallBack callBack) {getInstance().inner_postFormAsync(url, params, callBack);}/*** 建立网络框架，获取网络数据，异步post请求（json）** @param url      url* @param params   key value* @param callBack data*/public static void postJsonRequest(String url, Map<String, String> params, DataCallBack callBack) {getInstance().inner_postJsonAsync(url, params, callBack);}//-------------对外提供的方法End--------------------------------/*** 异步get请求（Form），内部实现方法** @param url    url* @param params key value*/private void inner_getFormAsync(String url, Map<String, String> params, final DataCallBack callBack) {if (params == null) {params = new HashMap<>();}// 请求url（baseUrl+参数）final String doUrl = urlJoint(url, params);// 新建一个请求final Request request = new Request.Builder().url(doUrl).build();//执行请求获得响应结果Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {deliverDataFailure(request, e, callBack);}@Overridepublic void onResponse(Call call, Response response) throws IOException {if (response.isSuccessful()) { // 请求成功//执行请求成功的操作String result = response.body().string();deliverDataSuccess(result, callBack);} else {throw new IOException(response + "");}}});}/*** 异步post请求（Form）,内部实现方法** @param url      url* @param params   params* @param callBack callBack*/private void inner_postFormAsync(String url, Map<String, String> params, final DataCallBack callBack) {RequestBody requestBody;if (params == null) {params = new HashMap<>();}FormBody.Builder builder = new FormBody.Builder();/*** 在这对添加的参数进行遍历*/for (Map.Entry<String, String> map : params.entrySet()) {String key = map.getKey();String value;/*** 判断值是否是空的*/if (map.getValue() == null) {value = "";} else {value = map.getValue();}/*** 把key和value添加到formbody中*/builder.add(key, value);}requestBody = builder.build();//结果返回final Request request = new Request.Builder().url(url).post(requestBody).build();okHttpClient.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {deliverDataFailure(request, e, callBack);}@Overridepublic void onResponse(Call call, Response response) throws IOException {if (response.isSuccessful()) { // 请求成功//执行请求成功的操作String result = response.body().string();deliverDataSuccess(result, callBack);} else {throw new IOException(response + "");}}});}/*** post请求传json** @param url      url* @param callBack 成功或失败回调* @param params     params*/private void inner_postJsonAsync(String url, Map<String, String> params,final DataCallBack callBack) {// 将map转换成json,需要引入Gson包String mapToJson = new Gson().toJson(params);final Request request = buildJsonPostRequest(url, mapToJson);okHttpClient.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {deliverDataFailure(request, e, callBack);}@Overridepublic void onResponse(Call call, Response response) throws IOException {if (response.isSuccessful()) { // 请求成功//执行请求成功的操作String result = response.body().string();deliverDataSuccess(result, callBack);} else {throw new IOException(response + "");}}});}/*** Json_POST请求参数** @param url  url* @param json json* @return requestBody*/private Request buildJsonPostRequest(String url, String json) {RequestBody requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), json);return new Request.Builder().url(url).post(requestBody).build();}/*** 分发失败的时候调用** @param request  request* @param e        e* @param callBack callBack*/private void deliverDataFailure(final Request request, final IOException e, final DataCallBack callBack) {/*** 在这里使用异步处理*/mHandler.post(new Runnable() {@Overridepublic void run() {if (callBack != null) {callBack.requestFailure(request, e);}}});}/*** 分发成功的时候调用** @param result   result* @param callBack callBack*/private void deliverDataSuccess(final String result, final DataCallBack callBack) {/*** 在这里使用异步线程处理*/mHandler.post(new Runnable() {@Overridepublic void run() {if (callBack != null) {try {callBack.requestSuccess(result);} catch (Exception e) {e.printStackTrace();}}}});}/*** 数据回调接口*/public interface DataCallBack {void requestSuccess(String result) throws Exception;void requestFailure(Request request, IOException e);}/*** 拼接url和请求参数** @param url    url* @param params key value* @return String url*/private static String urlJoint(String url, Map<String, String> params) {StringBuilder endUrl = new StringBuilder(url);boolean isFirst = true;Set<Map.Entry<String, String>> entrySet = params.entrySet();for (Map.Entry<String, String> entry : entrySet) {if (isFirst && !url.contains("?")) {isFirst = false;endUrl.append("?");} else {endUrl.append("&");}endUrl.append(entry.getKey());endUrl.append("=");endUrl.append(entry.getValue());}return endUrl.toString();}
}

NetRequest工具类的简单使用：

        String url = "网络请求的地址";HashMap<String, String> params = new HashMap<>();// 添加请求参数params.put("key", "value");// ...NetRequest.getFormRequest(url, params, new NetRequest.DataCallBack() {@Overridepublic void requestSuccess(String result) throws Exception {// 请求成功的回调}@Overridepublic void requestFailure(Request request, IOException e) {// 请求失败的回调}});

　　至于同步get、post请求同理，而且个人感觉使用较少，便没有写出，文件下载和上传同理。以上便是我对OKHttp的使用和认识，当然OKHttp远远不止这些，以后再慢慢补充。以上均为个人观点，如有错误，欢迎留言指出，以便及时修正。