Kotlin Retrofit response.body() returned null

Question

So I'm trying to fetch an API with endpoint https://someURL.com/someUrl/url?orderID=A001,

This is the returned JSON format as seen from Postman. So I use this Interface in the NetworkConfig.kt class to fetch this endpoint:

interface getOutstandingOrderDetail{
    @GET("url")
    fun getOutstandingOrderDetail(@Query("orderID") orderID: String): Call<OutstandingOrderDetailPOJODataClassData>
}

and store it in this data class (Generated by an Android Extension that generate POJO from JSON):

data class OutstandingOrderDetailPOJODataClass(

    @field:SerializedName("data")
    val data: OutstandingOrderDetailPOJODataClassData? = null,

    @field:SerializedName("error")
    val error: Error? = null
)

data class OutstandingOrderDetailPOJODataClassData(

    @field:SerializedName("Header")
    val header: OutstandingOrderDetailPOJODataClassHeader? = null,

    @field:SerializedName("Detail")
    val detail: List<OutstandingOrderDetailPOJODataClassDetailItem?>? = null
)

data class OutstandingOrderDetailPOJODataClassHeader(

    @field:SerializedName("buyer_address")
    val buyerAddress: String? = null,

    @field:SerializedName("total_price")
    val totalPrice: Int? = null,

    @field:SerializedName("buyer_name")
    val buyerName: String? = null,

    @field:SerializedName("status_confirmed_yn")
    val statusConfirmedYn: String? = null,

    @field:SerializedName("order_date")
    val orderDate: String? = null,

    @field:SerializedName("outlet_id")
    val outletId: String? = null,

    @field:SerializedName("nip")
    val nip: String? = null,

    @field:SerializedName("jumlah_product")
    val jumlahProduct: Int? = null,

    @field:SerializedName("last_update")
    val lastUpdate: String? = null,

    @field:SerializedName("phone_number")
    val phoneNumber: String? = null,

    @field:SerializedName("order_running_id")
    val orderRunningId: Int? = null,

    @field:SerializedName("status_tagged_yn")
    val statusTaggedYn: String? = null,

    @field:SerializedName("order_id")
    val orderId: String? = null
)

data class OutstandingOrderDetailPOJODataClassError(

    @field:SerializedName("msg")
    val msg: String? = null,

    @field:SerializedName("code")
    val code: Int? = null,

    @field:SerializedName("status")
    val status: Boolean? = null
)
data class OutstandingOrderDetailPOJODataClassDetailItem(

    @field:SerializedName("item_price_new")
    val itemPriceNew: Int? = null,

    @field:SerializedName("item_name_new")
    val itemNameNew: String? = null,

    @field:SerializedName("total_price")
    val totalPrice: Int? = null,

    @field:SerializedName("item_price")
    val itemPrice: Int? = null,

    @field:SerializedName("item_name")
    val itemName: String? = null,

    @field:SerializedName("status_refund")
    val statusRefund: String? = null,

    @field:SerializedName("detail_id")
    val detailId: Int? = null,

    @field:SerializedName("procode_new")
    val procodeNew: String? = null,

    @field:SerializedName("refund_date")
    val refundDate: String? = null,

    @field:SerializedName("request_refund")
    val requestRefund: String? = null,

    @field:SerializedName("procode")
    val procode: String? = null,

    @field:SerializedName("last_update")
    val lastUpdate: String? = null,

    @field:SerializedName("item_qty_new")
    val itemQtyNew: Int? = null,

    @field:SerializedName("order_id")
    val orderId: String? = null,

    @field:SerializedName("total_price_new")
    val totalPriceNew: Int? = null,

    @field:SerializedName("item_qty")
    val itemQty: Int? = null,

    @field:SerializedName("refund")
    val refund: Int? = null
)

This is a code snippet of the fragment where I fetch the URL data:

private fun fetchOrderedItemListData() {
    NetworkConfig()
        .getOutstandingDetailOrderedItemListService()
        .getOutstandingOrderDetailOrderedItemList("A001")
        .enqueue(object :
            Callback<OutstandingOrderDetailPOJODataClassData> {

            override fun onFailure(
                call: Call<OutstandingOrderDetailPOJODataClassData>,
                t: Throwable
            ) {
                Log.i("Order", "It Failed!!")

                if (call.isCanceled) {
                    Toast.makeText(
                        (activity as AppCompatActivity),
                        "Request Aborted",
                        Toast.LENGTH_SHORT
                    ).show()

                } else {
                    Toast.makeText(
                        (activity as AppCompatActivity),
                        t.localizedMessage,
                        Toast.LENGTH_SHORT
                    ).show()
                }
            }

            override fun onResponse(
                call: Call<OutstandingOrderDetailPOJODataClassData>,
                response: Response<OutstandingOrderDetailPOJODataClassData>
            ) {

                Log.i("Order", "Ordered Item FEtched -> \n ${response.body()}") <= This is for debugging purpose

                binding.rvOrderedItemList.adapter =
                    response.body()
                        ?.let { OrderedItemListAdapter(it, this@OrderDetailFragment) }

                binding.rvOrderedItemList.layoutManager =
                    LinearLayoutManager((activity as AppCompatActivity))

            }
        })
}

As you can see above I use Log.i to try to print the response.body() in the LogCat, However it returns null in the Log Cat. You can see it here.

Am I missing something ? If there's any detail that I left out for this question, feel free to ask.

Answer 1

Your Retrofit function is set up as:

    @GET("switch")
    fun getOutstandingOrderDetail(@Query("orderID") orderID: String): Call<OutstandingOrderDetailPOJODataClassData>

The data type in the Call<> needs to match your JSON. You have data classes that match your JSON... but the root of that hierarchy is OutstandingOrderDetailPOJODataClass, not OutstandingOrderDetailPOJODataClassData. So, change your Retrofit function to:

    @GET("switch")
    fun getOutstandingOrderDetail(@Query("orderID") orderID: String): Call<OutstandingOrderDetailPOJODataClass>