okhttp3.4.1+retrofit2.1.0实现离线缓存的示例

compile 'com.squareup.retrofit2:retrofit:2.1.0'
 compile 'com.squareup.retrofit2:converter-gson:2.1.0'
 compile 'com.squareup.okhttp3:okhttp:3.4.1'
 compile 'com.squareup.okhttp3:logging-interceptor:3.4.1'

File httpCacheDirectory = new File(Environment.getExternalStorageDirectory(), "HttpCache");//这里为了方便直接把文件放在了SD卡根目录的HttpCache中，一般放在context.getCacheDir()中
int cacheSize = 10 * 1024 * 1024;//设置缓存文件大小为10M
Cache cache = new Cache(httpCacheDirectory, cacheSize);
httpClient = new OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS)//设置连接超时
    .readTimeout(10, TimeUnit.SECONDS)//读取超时
    .writeTimeout(10, TimeUnit.SECONDS)//写入超时
    .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)//添加自定义缓存拦截器（后面讲解），注意这里需要使用.addNetworkInterceptor
    .cache(cache)//把缓存添加进来
    .build();

retrofit = new Retrofit.Builder()
    .baseUrl(baseUrl)
    .client(httpClient)//把OkHttpClient添加进来
    .addConverterFactory(GsonConverterFactory.create())
    .build();

 static Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
  @Override
  public Response intercept(Chain chain) throws IOException {
   Request request = chain.request();
   //网上很多示例代码都对在request请求前对其进行无网的判断，其实无需判断，无网自动访问缓存
//   if(!NetworkUtil.getInstance().isConnected()){
//    request = request.newBuilder()
//      .cacheControl(CacheControl.FORCE_CACHE)//只访问缓存
//      .build();
//   }
   Response respOnse= chain.proceed(request);
   if (NetworkUtil.getInstance().isConnected()) {
    int maxAge = 60;//缓存失效时间，单位为秒
    return response.newBuilder()
      .removeHeader("Pragma")//清除头信息，因为服务器如果不支持，会返回一些干扰信息，不清除下面无法生效
      .header("Cache-Control", "public ,max-age=" + maxAge)
      .build();
   } else {
    //这段代码设置无效
//    int maxStale = 60 * 60 * 24 * 28; // 无网络时，设置超时为4周
//    return response.newBuilder()
//      .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)
//      .removeHeader("Pragma")
//      .build();
   }
   return response;
  }
 };

@Headers("Cache-Control:public ,max-age=60")
@GET("getBusiness.action")//商店信息
Call getRestaurantInfo(@Query("userId") String userId,@Query("businessId") String businessId);

 static Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
  @Override
  public Response intercept(Chain chain) throws IOException {
   Request request = chain.request();
   Response respOnse= chain.proceed(request);
   if (NetworkUtil.getInstance().isConnected()) {
    //获取头部信息
    String cacheCOntrol=request.cacheControl().toString();
    return response.newBuilder()
      .removeHeader("Pragma")//清除头信息，因为服务器如果不支持，会返回一些干扰信息，不清除下面无法生效
      .header("Cache-Control", cacheControl)
      .build();
   }
   return response;
  }
 };

/**
 * 简单封装的Retroit初始化类
 */
public class initRetrofit {
 private static String baseUrl = "http://202.171.212.154:8080/hh/";
 private static OkHttpClient httpClient;
 private static Retrofit retrofit;
 public static Retrofit initRetrofit() {
  //缓存路径和大小
  File httpCacheDirectory = new File(Environment.getExternalStorageDirectory(), "HttpCache");
  int cacheSize = 10 * 1024 * 1024;
  Cache cache = new Cache(httpCacheDirectory, cacheSize);
  //日志拦截器
  HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
  interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
  httpClient = new OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS)//设置连接超时
    .readTimeout(10, TimeUnit.SECONDS)//读取超时
    .writeTimeout(10, TimeUnit.SECONDS)//写入超时
    .addInterceptor(interceptor)//添加日志拦截器
    .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)//添加缓存拦截器
    .cache(cache)//把缓存添加进来
    .build();
  retrofit = new Retrofit.Builder()
    .baseUrl(baseUrl)
    .client(httpClient)
    .addConverterFactory(GsonConverterFactory.create())
    .build();
  return retrofit;
 }

 public static RetrofitAPI getService() {
  return initRetrofit().create(RetrofitAPI.class);
 }

// //缓存拦截器，不同接口不同缓存
// static Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
//  @Override
//  public Response intercept(Chain chain) throws IOException {
//
//   Request request = chain.request();
//   Response respOnse= chain.proceed(request);
//
//   if (NetworkUtil.getInstance().isConnected()) {
//    String cacheCOntrol=request.cacheControl().toString();
//    return response.newBuilder()
//      .removeHeader("Pragma")//清除头信息，因为服务器如果不支持，会返回一些干扰信息，不清除下面无法生效
//      .header("Cache-Control", cacheControl)
//      .build();
//   }
//   return response;
//  }
// };
 //缓存拦截器，统一缓存60s
 static Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
  @Override
  public Response intercept(Chain chain) throws IOException {
   Request request = chain.request();
   Response respOnse= chain.proceed(request);
   if (NetworkUtil.getInstance().isConnected()) {
    int maxAge = 60*60*24*2;//缓存失效时间，单位为秒
    return response.newBuilder()
      .removeHeader("Pragma")//清除头信息，因为服务器如果不支持，会返回一些干扰信息，不清除下面无法生效
      .header("Cache-Control", "public ,max-age=" + maxAge)
      .build();
   }
   return response;
  }
 };
}