RetrofitClient.kt

class RetrofitClient(private val context: Context) {
    val cacheSize = (5 * 1024 * 1024).toLong()

    val instance: Api by lazy {
        val myCache = Cache(context.cacheDir, cacheSize)

        val okHttpClient = OkHttpClient.Builder()
            .cache(myCache)
            .addInterceptor { chain ->
                var request = chain.request()
                request = if (hasNetwork(context))
                    request
                        .newBuilder()
                        .cacheControl(
                            CacheControl.Builder()
                                .maxAge(30, TimeUnit.MINUTES)
                                .build()
                        )
                        .build()
                else
                    request
                        .newBuilder()
                        .cacheControl(
                            CacheControl.Builder()
                                .maxStale(1, TimeUnit.DAYS)
                                .build()
                        )
                        .build()
                chain.proceed(request)
            }
            .addInterceptor(HttpLoggingInterceptor().apply {
                this.level = HttpLoggingInterceptor.Level.BODY }
            )
            .build()

        val retrofit = Retrofit.Builder()
            .baseUrl("BASE_URL")
            .addConverterFactory(GsonConverterFactory.create())
            .client(okHttpClient)
            .build()

        retrofit.create(Api::class.java)
    }
}