how to paginate data using Room and RxJava?

Question

sopuse I have a function in my Room DAO like this:

@Query("SELECT * FROM cached_tbl ORDER BY id")
    fun getAll(): Flowable<List<Item>>

this returns all the items in the database but I don't want this, I want the data to be paginated and be emitted in little chunks. I want the data to be loaded from the database on demand, for example, 100 items per page. is there a way to do that?

Answer 1

Jetpack has a library for this called Paging which you might be interested in. The good thing about using Room is that it also has Paging integration, so setup will go something like:

Dao

@Query("SELECT * FROM cached_tbl ORDER BY id")
fun getAll(): PagingSource<Int, Item>

ViewModel

val pager = Pager(PagingConfig(pageSize)) { dao.getAll() }
  .cachedIn(viewModelScope)

Activity

lifecycleScope.launch {
  pager.flow.collectLatest {
    PagingDataAdapter.submtiData(it)
  }
}

You can read quite a bit more here: https://developer.android.com/topic/libraries/architecture/paging/v3-overview , including how to setup a layered source, transformations and more.