Update[24/04/19]:
I just found out that the library already provide us a way to listen to empty initial load, using PagedList.BoundaryCallback<YourItem>.
*Note that my old answer is still a valid alternative.
val livedPageList = LivePagedListBuilder(sourceFactory, config)
.setBoundaryCallback(object: PagedList.BoundaryCallback<YourItem>() {
override fun onZeroItemsLoaded() {
super.onZeroItemsLoaded()
// Handle empty initial load here
}
override fun onItemAtEndLoaded(itemAtEnd: YourItem) {
super.onItemAtEndLoaded(itemAtEnd)
// Here you can listen to last item on list
}
override fun onItemAtFrontLoaded(itemAtFront: YourItem) {
super.onItemAtFrontLoaded(itemAtFront)
// Here you can listen to first item on list
}
})
.build()
Original Answer:
Based on this class on google sample Network State. Modify it to handle empty content in initialLoad.
@Suppress("DataClassPrivateConstructor")
data class NetworkState private constructor(
val status: Status,
val msg: String? = null
) {
enum class Status {
RUNNING,
SUCCESS_LOADED, // New
SUCCESS_EMPTY, // New
FAILED
}
companion object {
val EMPTY = NetworkState(Status.SUCCESS_EMPTY) // New
val LOADED = NetworkState(Status.SUCCESS_LOADED) // New
val LOADING = NetworkState(Status.RUNNING)
fun error(msg: String?) = NetworkState(Status.FAILED, msg)
}
}
Usage as follow:
class DataSource: PageKeyedDataSource<Long, Item>() {
val initialLoad: MutableLiveData<NetworkState> = MutableLiveData()
override fun loadInitial(params: LoadInitialParams<Long>, callback: LoadInitialCallback<Long, Item>) {
initialLoad.postValue(NetworkState.LOADING)
apiCallSource.subscribe({ items ->
if (items.isEmpty()) {
initialLoad.postValue(NetworkState.EMPTY)
} else {
initialLoad.postValue(NetworkState.LOADED)
}
}, { error ->
// handle error
})
}
}
And this is how the activity handle it:
class activity: AppCompatActivity() {
val viewModel = // init viewmodel
override fun onCreate(savedInstanceState: Bundle?) {
viewModel.refreshState.observe(this, Observer { networkState ->
if (it == NetworkState.LOADING) {
// Show loading
} else {
// Hide loading
if (it.status == NetworkState.Status.SUCCESS_EMPTY) {
// Show empty state for initial load
}
}
}
}
}
For more details on how to connect DataSource with Activity, see this sample