использовать картинки с JSON не используя библиотеки

Как лучше выгрузить картинки из JSON в PhotoAdaper? Использую RecyclerView, создал отдельную функцию в ViewHolder. В Activity обработал загрузку альбома и фото, которые надо выгрузить из JSON.

class PhotosAdapter : RecyclerView.Adapter<PhotosAdapter.PhotosViewHolder>() {

    var photos: List<Photo> = mutableListOf()
        set(value) {
            field = value
            notifyDataSetChanged()
        }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PhotosViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(
                R.layout.item_photo,
                parent,
                false
        )
        return PhotosViewHolder(view)
    }

    override fun onBindViewHolder(holder: PhotosViewHolder, position: Int) {
        holder.bind(photos[position])
    }

    override fun getItemCount(): Int = photos.size

    class PhotosViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        private val imageViewPhoto: ImageView = itemView.findViewById(R.id.imageViewPhoto)
        private val textViewTitle: TextView = itemView.findViewById(R.id.textViewTitle)

        fun bind(photo: Photo) {
            textViewTitle.text = photo.title
            loadPhotoIntoImageView(photo.url, imageViewPhoto)
        }

        private fun loadPhotoIntoImageView(url: String, imageView: ImageView) {
            //Тут как-то надо загрузить фото в ImageView
        }
    }
}

Вот код из самой активности:

class PhotoActivity : AppCompatActivity() {

    private val mapper = Mapper()
    private val adapter = PhotosAdapter()

    private lateinit var recyclerViewPhotos: RecyclerView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_photo)
        recyclerViewPhotos = findViewById(R.id.recyclerViewPhotos)
        recyclerViewPhotos.adapter = adapter
        val id = intent.getIntExtra(EXTRA_USER_ID, -1)
        DownloadPhotosTask(id, adapter, mapper).execute()
    }

    class DownloadPhotosTask(
            private val userId: Int,
            private val adapter: PhotosAdapter,
            private val mapper: Mapper
    ) : AsyncTask<Void, Void, List<Photo>>() {
        override fun doInBackground(vararg params: Void?): List<Photo> {
            return try {
                val albumList = loadAlbum(userId)
                val albumIds = albumList.map { it.id }
                return loadPhotos(albumIds)
            } catch (e: Exception) {
                emptyList()
            }
        }

        override fun onPostExecute(result: List<Photo>?) {
            super.onPostExecute(result)
            if (result == null) return
            adapter.photos = result
        }

        private fun loadAlbum(userId: Int): List<Albums> {
            val url = URL("$LOAD_USER_ALBUM?${Albums.KEY_USERID}=$userId")
            val urlConnection = url.openConnection()
            val inputStreamReader = BufferedReader(
                    InputStreamReader(urlConnection.getInputStream())
            )
            val builder = StringBuilder()
            var line = inputStreamReader.readLine()
            while (line != null) {
                builder.append(line)
                line = inputStreamReader.readLine()
            }
            return mapper.mapJSONToAlbumsList(JSONArray(builder.toString()))
        }

        private fun loadPhotos(albumIds: List<Int>): List<Photo> {
            val idsToPhotoUrlBuilder = StringBuilder()
            for (i in albumIds.indices) {
                if (i == 0) {
                    idsToPhotoUrlBuilder.append("?")
                } else {
                    idsToPhotoUrlBuilder.append("&")
                }
                idsToPhotoUrlBuilder.append("${Photo.KEY_ALBUMID}=${albumIds[i]}")
            }
            val url = URL(LOAD_USER_PHOTO + idsToPhotoUrlBuilder.toString())
            val urlConnection = url.openConnection()
            val inputStreamReader = BufferedReader(
                    InputStreamReader(urlConnection.getInputStream())
            )
            val builder = StringBuilder()
            var line = inputStreamReader.readLine()
            while (line != null) {
                builder.append(line)
                line = inputStreamReader.readLine()
            }
            return mapper.mapJSONToPhotoList(JSONArray(builder.toString()))
        }
    }

    companion object {
        const val EXTRA_USER_ID = "extra_user_id"

        const val LOAD_USER_PHOTO = "https://jsonplaceholder.typicode.com/photos"
        private const val LOAD_USER_ALBUM = "https://jsonplaceholder.typicode.com/albums"

        fun newIntent(context: Context, userId: Int): Intent {
            val intent = Intent(context, PhotoActivity::class.java)
            intent.putExtra(EXTRA_USER_ID, userId)
            return intent
        }
    }
}