Jetpack Paging 3.0 with Airbnb/epoxy only load the first page - kotlin

Question

I am trying to use Jetpack Paging 3.0 to get all the characters in Rick and Morty API using retrofit and display it using Airbnb/epoxy. But I only get the first page I've spent several hours trying to look for a solution but no luck.
Link to API
(Rick and Morty API)
CODE:
1 Retrofit
#GET("character/")
suspend fun getAllCharactersByPage(
#Query("page") pageIndex : Int
): Response<GetAllCharactersByPageResponse>
[2] Paging Source
class AllCharacterPagingSource(
private val repository: AllCharactersRepository) : PagingSource<Int, Character>() {
override suspend fun load(
params: LoadParams<Int>
): LoadResult<Int, Character> {
val pageNumber = params.key ?: 1
val prevKey = if (pageNumber == 1) null else pageNumber + 1
val response = NetworkLayer.apiClient.getAllCharactersByPage(pageNumber)
response.getException?.let {
return LoadResult.Error(it)
}
return LoadResult.Page(
data = response.body.results.map { CharacterMapper.buildFrom(it) },
prevKey = prevKey,
nextKey = getPageIndexFromNext(response.body.info.next)
)
}
override fun getRefreshKey(state: PagingState<Int, Character>): Int? {
return state.anchorPosition?.let {
state.closestPageToPosition(it)?.prevKey?.plus(1)
?: state.closestPageToPosition(it)?.nextKey?.minus(1)
}
}
private fun getPageIndexFromNext(next: String?): Int?{
return next?.split("?page=")?.get(1)?.toInt()
}
}
[3] View Model (Pager)
class AllCharactersViewModel : ViewModel() {
private val repository = AllCharactersRepository()
val flow = Pager(
PagingConfig(Constants.PAGE_SIZE, Constants.PREFETCH_SIZE, enablePlaceholders = false)
) {
AllCharacterPagingSource(repository)
}.flow.cachedIn(viewModelScope)
}
[4] Fragment (Submitting data)
iewLifecycleOwner.lifecycleScope.launch {
allCharactersViewModel.flow.collectLatest {
pagingEpoxyController.submitData(it)
}
}
binding.charactersEpoxyRecyclerView.setController(pagingEpoxyController)
[5] Epoxy Controller
class CharactersPagingEpoxyController : PagingDataEpoxyController<Character>() {
var context : Context? = null
override fun buildItemModel(currentPosition: Int, item: Character?): EpoxyModel<*> {
return CharacterCardModel(
character = item!!,
context = context!!,
onClick = { characterId ->
}
).id("characters_${item.id}")
}
data class CharacterCardModel(
val character : Character,
val context : Context,
val onClick: (Int) -> Unit
) : ViewBindingKotlinModel<CharacterCardContainerModelBinding>(R.layout.character_card_container_model) {
override fun CharacterCardContainerModelBinding.bind() {
Glide.with(context)
.load(character.image)
.into(imageView)
characterName.text = character.name
mirroredCharacterName.text = character.name
}
}
}
Thanks in advance!!!

Answer 1

I guess prevKey should be something like this
val previewPage= if (pageNumber ==1 ) null else pageNumber -1