public class OkHttp3BasicActivity extends Activity {@BindView(R.id.sn_tv)TextView tv;private OkHttpClient client ;String str = "";private Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {super.handleMessage(msg);switch (msg.what){case 1:tv.setText(msg.obj.toString());break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.simple_network_main);ButterKnife.bind(this);new Thread(new Runnable() {@Overridepublic void run() {okrun();}}).start();}private void okrun(){client = new OkHttpClient();httpUrl = httpUrl+"?"+httpArg;Request request = new Request.Builder().url("http://publicobject.com/helloworld.txt").build();client.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);str = response.body().string();Message msg = Message.obtain();msg.what =1;msg.obj = str;handler.sendMessage(msg);}});}
}

• 创建OkHttpClient对象。OkHttpClient为网络请求执行的一个中心，它会管理连接池，缓存，SocketFactory，代理，各种超时时间，DNS，请求执行结果的分发等许多内容。
• 创建Request对象。Request用于描述一个HTTP请求，比如请求的方法是"GET"还是"POST"，请求的URL，请求的header，请求的body，请求的缓存策略等。
• 利用前面创建的OkHttpClient对象和Request对象创建Call对象。Call是一次HTTP请求的Task，它会执行网络请求以获得响应。OkHttp中的网络请求执行Call既可以同步进行，也可以异步进行。调用call.execute()将直接执行网络请求，阻塞直到获得响应。而调用call.enqueue()传入回调，则会将Call放入一个异步执行队列，由ExecutorService在后台执行。

private Response getResponseWithInterceptorChain() throws IOException {  //构建全栈拦截器  List interceptors = new ArrayList<>();  interceptors.addAll(client.interceptors());//自定义拦截器  interceptors.add(retryAndFollowUpInterceptor);//重试拦截器  interceptors.add(new BridgeInterceptor(client.cookieJar()));//桥接拦截器  interceptors.add(new CacheInterceptor(client.internalCache()));//缓存拦截器  interceptors.add(new ConnectInterceptor(client));//连接拦截器  if (!retryAndFollowUpInterceptor.isForWebSocket()) {  interceptors.addAll(client.networkInterceptors());//用户预定义的网络拦截器
    }  interceptors.add(new CallServerInterceptor(  retryAndFollowUpInterceptor.isForWebSocket()));//调用服务拦截器  //内部通过责任链模式来使用拦截器  Interceptor.Chain chain = new RealInterceptorChain(  interceptors, null, null, null, 0, originalRequest);  return chain.proceed(originalRequest);//获取Response  }  

public final class RealInterceptorChain implements Interceptor.Chain {private final List<Interceptor> interceptors;private final StreamAllocation streamAllocation;private final HttpStream httpStream;private final Connection connection;private final int index;private final Request request;private int calls;public RealInterceptorChain(List<Interceptor> interceptors, StreamAllocation streamAllocation,HttpStream httpStream, Connection connection, int index, Request request) {this.interceptors = interceptors;this.connection = connection;this.streamAllocation = streamAllocation;this.httpStream = httpStream;this.index = index;this.request = request;}

RealInterceptorChain next = new RealInterceptorChain(interceptors, streamAllocation, httpStream, connection, index + 1, request);Interceptor interceptor = interceptors.get(index);Response response = interceptor.intercept(next);

@Override public Response intercept(Chain chain) throws IOException {  RealInterceptorChain realChain = (RealInterceptorChain) chain;  Request request = realChain.request();  StreamAllocation streamAllocation = realChain.streamAllocation();  // We need the network to satisfy this request. Possibly for validating a conditional GET.  boolean doExtensiveHealthChecks = !request.method().equals("GET");  HttpStream httpStream = streamAllocation.newStream(client, doExtensiveHealthChecks);  RealConnection connection = streamAllocation.connection();  return realChain.proceed(request, streamAllocation, httpStream, connection);  }