ProgressLayout | custom progress layout view for Android | Android library

class FavouritesFragment : Fragment() {
lateinit var recyclerFavourite:RecyclerView
lateinit var progressLayout:RelativeLayout
lateinit var progressBar:ProgressBar
lateinit var layoutManager:RecyclerView.LayoutManager
lateinit var recyclerAdapter: FavouriteRecyclerAdapter
var dbBookList=listOf()


override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    val view=inflater.inflate(R.layout.fragment_favourites, container, false)
    recyclerFavourite=view.findViewById(R.id.recyclerFavourite)
    progressLayout=view.findViewById(R.id.progressLayout)
    progressBar=view.findViewById(R.id.progressBar)
    layoutManager=GridLayoutManager(activity as Context,2)
    dbBookList=RetrieveFavourites(activity as Context).execute().get()
    if(activity!=null)
    {
        progressLayout.visibility=View.GONE
        recyclerAdapter= FavouriteRecyclerAdapter(activity as Context,dbBookList)
        recyclerFavourite.adapter=recyclerAdapter
        recyclerFavourite.layoutManager=layoutManager
    }
    return view
}
class RetrieveFavourites(val context: Context):AsyncTask>()
{
    override fun doInBackground(vararg p0: Void?): List {
        val db= Room.databaseBuilder(context,BookDatabase::class.java,"books-db").build()
        return db.bookDao().getAllBooks()
    }

}