NetworkingModuleUtils.java

package com.facebook.react.modules.network;

import com.facebook.react.bridge.ReactApplicationContext;

import java.io.IOException;

import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class NetworkingModuleUtils {
    public static NetworkingModule createNetworkingModuleWithCustomClient(ReactApplicationContext context) {
        OkHttpClient client = OkHttpClientProvider.createClient();

        OkHttpClient customClient = client.newBuilder()
            .addNetworkInterceptor(new Interceptor() {
                @Override
                public Response intercept(Chain chain) throws IOException {
                    Request request = chain.request();
                    String contentType = request.header("Content-Type");
                    Request customRequest = "application/json; charset=utf-8".equals(contentType) ?
                        request.newBuilder()
                            .header("content-type", "application/json")
                            .build() : request;

                    Response response = chain.proceed(customRequest);
                    return response;
                }
            }).build();

        return new NetworkingModule(context, null, customClient);
    }
}