A simple app that uses PageKeyedDataSource from Android Paging Library. It uses the Github API for searching users.
Use GithubPageKeyedDataSource to loadInitial and loadAfter.
/**
* A data source that uses the before/after keys returned in page requests.
*/
class GithubPageKeyedDataSource : PageKeyedDataSource<Int, Item>() {
override fun loadInitial(params: LoadInitialParams<Int>,
callback: LoadInitialCallback<Int, Item>) {
val currentPage = 1
val nextPage = currentPage + 1
val request = githubApi.searchUsers(
query = searchQuery,
page = currentPage,
perPage = params.requestedLoadSize)
// Retrofit Call onResponse omitted
callback.onResult(items, null, nextPage)
}
override fun loadAfter(params: LoadParams<Int>,
callback: LoadCallback<Int, Item>) {
val currentPage = params.key
val nextPage = currentPage + 1
val request = githubApi.searchUsersAsync(
query = searchQuery,
page = currentPage,
perPage = params.requestedLoadSize)
// Retrofit Call onResponse omitted
callback.onResult(items, nextPage)
}
}Create a GithubDataSourceFactory.
class GithubDataSourceFactory(
private val searchQuery: String,
private val githubApi: GithubApiService,
private val retryExecutor: Executor
) : DataSource.Factory<Int, Item>() {
val source = MutableLiveData<GithubPageKeyedDataSource>()
override fun create(): DataSource<Int, Item> {
val source = GithubPageKeyedDataSource(searchQuery, githubApi, retryExecutor)
this.source.postValue(source)
return source
}
}Hook it up with your InMemoryByPageKeyRepository.
class InMemoryByPageKeyRepository(
private val githubApi: GithubApiService,
private val networkExecutor: Executor
) : GithubRepository {
@MainThread
override fun searchUsers(searchQuery: String, pageSize: Int): Listing<Item> {
val factory = githubDataSourceFactory(searchQuery)
val config = pagedListConfig(pageSize)
val livePagedList = LivePagedListBuilder(factory, config)
.setFetchExecutor(networkExecutor)
.build()
return Listing(
pagedList = livePagedList,
networkState = switchMap(factory.source) { it.network },
retry = { factory.source.value?.retryAllFailed() },
refresh = { factory.source.value?.invalidate() },
refreshState = switchMap(factory.source) { it.initial })
}
private fun githubDataSourceFactory(searchQuery: String): GithubDataSourceFactory {
return GithubDataSourceFactory(searchQuery, githubApi, networkExecutor)
}
private fun pagedListConfig(pageSize: Int): PagedList.Config {
return PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setInitialLoadSizeHint(pageSize * 2)
.setPageSize(pageSize)
.build()
}
}Call searchUsers from the SearchUsersViewModel:
class SearchUsersViewModel(
private val repository: GithubRepository
) : ViewModel() {
private val searchQuery = MutableLiveData<String>()
private val itemResult = map(searchQuery) {
repository.searchUsers(it, PAGE_SIZE)
}
val items = switchMap(itemResult) { it.pagedList }!!
val networkState = switchMap(itemResult) { it.networkState }!!
val refreshState = switchMap(itemResult) { it.refreshState }!!
...
}Thanks for stopping by! :)