Example Android Application with OkHTTP and Retrofit with Caching

MyApplication.java

import android.app.Application;
import android.util.Log;
import com.bahadirakin.service.UserService;
import com.bahadirakin.util.Constants;
import com.bahadirakin.util.LoggingInterceptor;
import com.bahadirakin.util.NetworkUtil;
import com.squareup.okhttp.Cache;
import com.squareup.okhttp.OkHttpClient;
import retrofit.RequestInterceptor;
import retrofit.RestAdapter;
import retrofit.client.OkClient;

import java.io.File;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class MyApplication extends Application {

    private UserService userService;

    public void onCreate() {
        initializeServices();
    }

    private void initializeServices() {
        Log.i("MyApplication", "TempDir: " + System.getProperty("java.io.tmodir"));
        final File cacheDir = new File(System.getProperty("java.io.tmpdir"), "my.cache");
        Log.i("MyApplication", "CacheDirExists?: " + cacheDir.exists());
        final Cache cache = new Cache(cacheDir, 10 * 1024 * 1024);

        final OkHttpClient okHttpClient = new OkHttpClient();
        okHttpClient.setCache(cache);
        okHttpClient.networkInterceptors().add(new LoggingInterceptor());

        final Executor executor = Executors.newCachedThreadPool();

        final RestAdapter restAdapter = new RestAdapter.Builder()
                .setExecutors(executor, executor)
                .setEndpoint(Constants.SERVICE_BASE_URL)
                .setClient(new OkClient(okHttpClient))
                .setRequestInterceptor(new RequestInterceptor() {
                    @Override
                    public void intercept(RequestFacade request) {
                        if (!NetworkUtil.isOnline(getApplicationContext())) {
                            int maxStale = 60 * 60 * 24 * 7;
                            request.addHeader("Cache-Control", "public, only-if-cached, max-stale=" + maxStale);
                        }
                    }
                })
                .build();

        userService = restAdapter.create(UserService.class);
    }

    public UserService getUserService() {
        return userService;
    }
}