CODEWITHSUNDEEP
androidkotlinandroid-pagingandroid-paging-libraryandroid-paging-3
Florian Walther
Florian Walther

Reputation: 6961

Paging 3 - Why does my retry footer not call my PagingSource's load method?

I've implemented Paging 3 into my app following a codelab and added a footer with a retry button via withLoadStateHeaderAndFooter:

recycler_view_results.adapter = adapter.withLoadStateHeaderAndFooter(
    header = UnsplashLoadStateAdapter { adapter.retry() },
    footer = UnsplashLoadStateAdapter { adapter.retry() }
)

When I click the retry button in my footer's ViewHolder, adapter.retry() is indeed called, so the setup there is correct. However, this method never ends up calling my PagingSource's load method as it normally should.

My PagingSource (I checked that the LoadResult.Error is returned correctly in an error case):

class UnsplashPagingSource(
    private val unsplashApi: UnsplashApi,
    private val query: String
) : PagingSource<Int, UnsplashPhoto>() {
    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, UnsplashPhoto> {
        val position = params.key ?: UNSPLASH_STARTING_PAGE_INDEX
        return try {
            val response = unsplashApi.searchPhotos(query, position, params.loadSize)
            val photos = response.results
            LoadResult.Page(
                data = photos,
                prevKey = if (position == UNSPLASH_STARTING_PAGE_INDEX) null else position - 1,
                nextKey = if (photos.isEmpty()) null else position + 1
            )
        } catch (exception: IOException) {
            return LoadResult.Error(exception)
        } catch (exception: HttpException) {
            return LoadResult.Error(exception)
        }
    }
}

My repository:

class UnsplashRepository @Inject constructor(private val unsplashApi: UnsplashApi) {

    fun getSearchResultStream(query: String): Flow<PagingData<UnsplashPhoto>> {
        return Pager(
            config = PagingConfig(
                pageSize = NETWORK_PAGE_SIZE,
                enablePlaceholders = false
            ),
            pagingSourceFactory = { UnsplashPagingSource(unsplashApi, query) }
        ).flow
    }

    companion object {
        private const val NETWORK_PAGE_SIZE = 20
    }
}

And in my fragment I do this:

private fun searchPhotos(query: String) {
    searchJob?.cancel()
    searchJob = lifecycleScope.launch {
        viewModel.searchPhotos(query).collectLatest {
            adapter.submitData(it)
        }
    }
}

Interestingly the retry button for an empty list works:

retry_button.setOnClickListener {
    adapter.retry()
    // this works
}

Upvotes: 1

Views: 3478

Answers (1)

Florian Walther
Florian Walther

Reputation: 6961

It works now after I updated the paging dependency from '3.0.0-alpha02' to '3.0.0-alpha03'. Looks like this was a bug in the library.

Afterward I also found the corresponding bug report: https://issuetracker.google.com/issues/160194384

Upvotes: 1

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