paging

Paging 3 for Android and Compose

Adapted from Meet-Miyani/compose-skill's Paging references. MIT licensed. Related: android-skills:android-data-layer (non-paged repository), android-skills:android-retrofit / android-skills:kmp-ktor (network feeding PagingSource), android-skills:compose (LazyColumn).

This reference covers the current-version fact, the placement and identity rules that are easy to get wrong, and the RemoteMediator offline-first timing — not the basics of PagingSource / Pager / collectAsLazyPagingItems.

Version (current fact)

As of androidx.paging 3.5.0, paging-common, paging-compose, and paging-testing are Kotlin Multiplatform (Android, JVM, iOS, Native, JS/Wasm); only paging-runtime (and -guava/-rxjava) stay Android-only. So in a clean-architecture domain module, depend only on androidx.paging:paging-common — it ships PagingSource / PagingData / LoadResult with no Android dependency, so PagingSource interfaces and use cases can live in domain. (Verify the current version and KMP support at the releases page.)

Dual-flow rule — PagingData is its own Flow, never a field in UiState

Expose uiState: StateFlow<UiState> AND pagingItems: Flow<PagingData<T>> as separate properties.

val uiState: StateFlow<UiState> = _uiState.asStateFlow()
val pagingItems: Flow<PagingData<RepoUi>> =
    Pager(PagingConfig(pageSize = 20, prefetchDistance = 5, enablePlaceholders = false)) { repo.repoPagingSource() }
        .flow
        .map { data -> data.map { it.toUi() } }   // transforms BEFORE cachedIn
        .cachedIn(viewModelScope)

If PagingData rides inside UiState, every non-paging state change (selection, filter chip, snackbar) re-emits UiState and hands collectAsLazyPagingItems() a brand-new Flow<PagingData> — it drops its cache, restarts loads, and resets scroll to top.