可以在脱机时使用缓存数据用OKHttp进行改装吗

Question

File httpCacheDirectory = new File(context.getCacheDir(), "responses");

HttpResponseCache httpResponseCache = null;
try {
     httpResponseCache = new HttpResponseCache(httpCacheDirectory, 10 * 1024 * 1024);
} catch (IOException e) {
     Log.e("Retrofit", "Could not create http cache", e);
}

OkHttpClient okHttpClient = new OkHttpClient();
okHttpClient.setResponseCache(httpResponseCache);

api = new RestAdapter.Builder()
          .setEndpoint(API_URL)
          .setLogLevel(RestAdapter.LogLevel.FULL)
          .setClient(new OkClient(okHttpClient))
          .build()
          .create(MyApi.class);

public interface MyApi {
   @Headers("Cache-Control: public, max-age=640000, s-maxage=640000 , max-stale=2419200")
   @GET("/api/v1/person/1/")
   void requestPerson(
           Callback<Person> callback
   );

编辑：由于OKHttp 2.0.xHttpResponSecache是Cache，SetResponSecache是SetCache

Answer 1

OkHttp拦截器是脱机时访问缓存的正确方式：

1）创建拦截器：

private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
    @Override public Response intercept(Chain chain) throws IOException {
        Response originalResponse = chain.proceed(chain.request());
        if (Utils.isNetworkAvailable(context)) {
            int maxAge = 60; // read from cache for 1 minute
            return originalResponse.newBuilder()
                    .header("Cache-Control", "public, max-age=" + maxAge)
                    .build();
        } else {
            int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
            return originalResponse.newBuilder()
                    .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)
                    .build();
        }
    }

2）安装客户端：

OkHttpClient client = new OkHttpClient();
client.networkInterceptors().add(REWRITE_CACHE_CONTROL_INTERCEPTOR);

//setup cache
File httpCacheDirectory = new File(context.getCacheDir(), "responses");
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(httpCacheDirectory, cacheSize);

//add cache to the client
client.setCache(cache);

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(BASE_URL)
        .client(client)
        .addConverterFactory(GsonConverterFactory.create())
        .build();

        File httpCacheDirectory = new File(context.getCacheDir(), "responses");

        Cache cache = null;
        try {
            cache = new Cache(httpCacheDirectory, 10 * 1024 * 1024);
        } catch (IOException e) {
            Log.e("OKHttp", "Could not create http cache", e);
        }

        OkHttpClient okHttpClient = new OkHttpClient();
        if (cache != null) {
            okHttpClient.setCache(cache);
        }
        String hostURL = context.getString(R.string.host_url);

        api = new RestAdapter.Builder()
                .setEndpoint(hostURL)
                .setClient(new OkClient(okHttpClient))
                .setRequestInterceptor(/*rest of the answer here */)
                .build()
                .create(MyApi.class);

RestAdapter.Builder builder= new RestAdapter.Builder()
   .setRequestInterceptor(new RequestInterceptor() {
        @Override
        public void intercept(RequestFacade request) {
            request.addHeader("Accept", "application/json;versions=1");
            if (MyApplicationUtils.isNetworkAvailable(context)) {
                int maxAge = 60; // read from cache for 1 minute
                request.addHeader("Cache-Control", "public, max-age=" + maxAge);
            } else {
                int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
                request.addHeader("Cache-Control", 
                    "public, only-if-cached, max-stale=" + maxStale);
            }
        }
});