PhotoRepository-1.kt

private val executor: ExecutorService = Executors.newSingleThreadExecutor()
private val handler: Handler = Handler(Looper.getMainLooper())
interface Callback {
    fun onFinished(photoListPage: PhotoListPage)
}
private val adapter = PhotoAdapter()
override fun search(term: String, page: Int, callback: Callback) {
    executor.submit {
        val apiResponse = flickrService.search(apiKey, term, PERPAGE, page)
        callback.onFinished(PhotoListPage(term, page, apiResponse.photos.photo.map(adapter::convert), page < apiResponse.photos.pages))
    }
}