Understanding Android Paging Library: DataSource, PagedList, and PagedListAdapter

Paging Library is an Android Architecture Component that provides a structured way to load large data sets in pages, improving UI performance and user experience.

The library consists of three core classes: DataSource , PagedList , and PagedListAdapter . DataSource defines how data is fetched and comes in three generic forms: PageKeyedDataSource , ItemKeyedDataSource , and PositionalDataSource , each suited for different pagination scenarios.

PagedList is a List subclass that holds loaded items and manages prefetching, placeholders, and configuration via Config (pageSize, prefetchDistance, initialLoadSizeHint, enablePlaceholders). It stores data in a PagedStorage structure and notifies observers when new pages arrive.

PagedListAdapter extends RecyclerView.Adapter to bind a PagedList to a UI. It works with PagedListAdapterHelper and ListAdapterConfig to automatically compute diffs and refresh the RecyclerView without manual calls to notifyDataSetChanged() .

Data can be loaded from a single source (local DB or network) using LivePagedListBuilder to produce LiveData<PagedList> , or from multiple sources by attaching a BoundaryCallback that triggers network fetch after the local data is exhausted.

The library handles thread switching, background loading, and placeholder management internally, allowing developers to focus on the actual data retrieval logic while delivering smoother scrolling experiences.