ContiguousPagedList onPageError while I'm not using ContiguousPagedList

Question

I have implementation of PositionalDataSource that defines loadInitial and loadRange. Paging works fine however under some boundary condition (likely related with loading next page in progress while exiting the screen) app crashes with androidx.paging.ContiguousPagedList$1.onPageError (ContiguousPagedList.java:153). However a per https://developer.android.com/reference/android/arch/paging/PositionalDataSource my source is not contiguous?

Crash occurs under ContiguousPagedList's onPageError, line with "todo":

public void onPageError(@PageResult.ResultType int resultType,
        @NonNull Throwable error, boolean retryable) {

   LoadState errorState = retryable ? LoadState.RETRYABLE_ERROR : LoadState.ERROR;

    if (resultType == PageResult.PREPEND) {
        mLoadStateManager.setState(LoadType.START, errorState, error);
    } else if (resultType == PageResult.APPEND) {
        mLoadStateManager.setState(LoadType.END, errorState, error);
    } else {
        // TODO: pass init signal through to *previous* list
        throw new IllegalStateException("TODO");
    }
}

My configuration is not using placeholders, and I'm not passing total count into onResult of LoadInitialCallback. Version of paging library is 2.1.1

Answer 1

I experienced the same behaviour because I called callback.onError(e) when an exception happened in loadInitial and loadAfter methods of my PageKeyedDataSource implementation. In order to prevent the app from crashing I removed the callback.onError(e) line. I know this is not a solution, but at least my app is not crashing randomly.

Example code (Kotlin+coroutines incoming)

override fun loadInitial(params: LoadInitialParams<Long>, callback: LoadInitialCallback<Long, Beer>) {
    scope.launch {
        try {
            val response =
                BackendService.client.getBeers(
                    name = searchQueryNullable,
                    page = 1,
                    pageSize = params.requestedLoadSize
                )
            callback.onResult(response, 1, 2)
        } catch (e: Exception) {
            Log.e(tag, "Error loadInitial", e)
            // callback.onError(e) <-- this is the line that generates the crash: comment it
        }
    }
}