Implementation of MainReactPackage thats creates a custom NetworkingModule that configures an HTTP cache.

MainReactPackageWithHttpCache.java

package com.cachetester;

import com.facebook.react.bridge.ModuleSpec;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.modules.network.NetworkingModule;
import com.facebook.react.modules.network.OkHttpClientProvider;
import com.facebook.react.shell.MainReactPackage;

import java.io.File;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.List;

import javax.inject.Provider;

import okhttp3.Cache;
import okhttp3.OkHttpClient;

public class MainReactPackageWithHttpCache extends MainReactPackage {

  @Override
  public List<ModuleSpec> getNativeModules(ReactApplicationContext context) {
    List<ModuleSpec> originalNativeModules = super.getNativeModules(context);
    List<ModuleSpec> customNativeModules = new ArrayList<>();

    ModuleSpec customNetworkingModuleSpec = createNetworkingModuleSpecWithHttpCache(context);

    for (ModuleSpec originalModuleSpec : originalNativeModules) {
      if (originalModuleSpec.getType().equals(NetworkingModule.class)) {
        customNativeModules.add(customNetworkingModuleSpec);
      } else {
        customNativeModules.add(originalModuleSpec);
      }
    }

    return customNativeModules;
  }

  private ModuleSpec createNetworkingModuleSpecWithHttpCache(final ReactApplicationContext context) {
    return new ModuleSpec(NetworkingModule.class, new Provider<NativeModule>() {
      @Override
      public NativeModule get() {
        try {
          Constructor constructorWithOkClient =
              NetworkingModule.class.getDeclaredConstructor(
                  ReactApplicationContext.class,
                  String.class,
                  OkHttpClient.class);
          constructorWithOkClient.setAccessible(true);
          return (NetworkingModule) constructorWithOkClient.newInstance(
              context,
              null,
              createOkHttpClientWithCache(context));
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
    });
  }

  private OkHttpClient createOkHttpClientWithCache(ReactApplicationContext context) {
    return OkHttpClientProvider.createClient().newBuilder()
        .cache(new Cache(new File(context.getCacheDir(), "http-cache"), 50 * 1024 * 1024))
        .build();
  }
}