Challenge : Adding a custom GSON Deserialiszer

Android Programming (4th Edition) 24. HTTP and Background Tasks
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This is honestly the only way I was able to do this. Please if you see any mistake or if there is any way you think I can improve on this, I’m all ears. The only issue with this solution is that I am not exactly sure what the web request is returning because I specified a lateint var property named “photos” in the custom deserialization file to be a able to reference it from FlickeFetchr and when I change it to photo, the app crashes saying it hasn’t been initialized (as if no request was returned??). So I got all confused and tired from the researching and this is what I was able to come out with.

import com.bignerdranch.android.photogallery.api.PhotoResponse
import com.google.gson.Gson
import com.google.gson.JsonDeserializationContext
import com.google.gson.JsonDeserializer
import com.google.gson.JsonElement
import java.lang.reflect.Type

// OUR CUSTOM JSON DESERIALIZER FILE

class PhotoDeserializer: JsonDeserializer {

lateinit var photos : PhotoResponse // the property

override fun deserialize(
    json: JsonElement?,
    typeOfT: Type?,
    context: JsonDeserializationContext?
): PhotoResponse {
    val photoJsonObject = json?.asJsonObject
    val gson = Gson()

    return gson.fromJson(photoJsonObject, PhotoResponse::class.java)
}

}

Our custom converter factory

init {
val gsonPhotoDeserializer = GsonBuilder() // Our Gson instance
.registerTypeAdapter(PhotoResponse::class.java, PhotoDeserializer())
.create()

    // custom converter factory
    val customGsonConverterFactory = GsonConverterFactory.create(gsonPhotoDeserializer)
    
    val retrofit : Retrofit = Retrofit.Builder()
        .baseUrl("https://api.flickr.com/")  // the baseUrl is our request endpoint
        .addConverterFactory(customGsonConverterFactory)
        .build()

    flickrApi = retrofit.create(FlickrApi::class.java)
}

fun fetchPhotos(): LiveData<List> {
val responseLiveData: MutableLiveData<List> = MutableLiveData()
val flickrRequest: Call = flickrApi.fetchPhotos()

    flickrRequest.enqueue(object: Callback<PhotoDeserializer> {
        override fun onFailure(call: Call<PhotoDeserializer>, t: Throwable) {
            Log.e(TAG, "Failed to fetch photos", t)
        }

        override fun onResponse(
            call: Call<PhotoDeserializer>,
            response: Response<PhotoDeserializer>
        ) {
            // This whole block of code digs the galleryItem list out of the response and updates the live data object with the list(photos).
            Log.d(TAG,"Response received $response")
            val flickrResponse: PhotoDeserializer? = response.body()
            val photoResponse: PhotoResponse? = flickrResponse?.photos  // Where I had to reference photos
            var galleryItems: List<GalleryItem> = photoResponse?.galleryItems
                ?: mutableListOf()
            galleryItems = galleryItems.filterNot {
                it.url.isBlank()
            }
            responseLiveData.value = galleryItems
        }
    })
    return responseLiveData
}