// Retrofit 网络数据请求

    public static RetrofitAPI Retrofit() {

        if (retrofitAPI == null) {

            retrofitAPI = new Retrofit.Builder()

                    .baseUrl(ApkManager.baseUrl)

                    .addConverterFactory(GsonConverterFactory.create())

                    .client(genericClient())

                    .build()

                    .create(RetrofitAPI.class);

        }

        return retrofitAPI;

    }

    public static String date = ""; //记录版本发布时间

    public static OkHttpClient genericClient() {

        OkHttpClient httpClient = new OkHttpClient.Builder()

                .addInterceptor(new Interceptor() {

                    @Override

                    public Response intercept(Chain chain) throws IOException {

                        Request request = chain.request()

                                .newBuilder()

                                .addHeader("User-Agent", "xxxx/xxxx/"+date)

                                .build();

                        return chain.proceed(request);

                    }

                }).connectTimeout(, TimeUnit.SECONDS).      // 设置连接超时时间

                readTimeout(, TimeUnit.SECONDS).

                writeTimeout(, TimeUnit.SECONDS).build(); 

        return httpClient;

    }