Following this codelab I have implemented pagination and caching using RemoteMediator (I am calling a simple API that returns a list of news). I am injecting this RemoteMediator to Repository which has method getResultStream() that returns Flow<PagingData<News>>. In ViewModel is function getNews() : Flow<PagingData<News>> and in Fragment I am calling this function and submitting list to RecyclerAdapter.
Now I want to add a new API call that returns news but with search keyword. What is the proper way to do it? Do I have to write all this code again and create a new RemoteMediator? The logic will be the same but now I have to pass a string argument to the Retrofit get function. The result of this call will replace items in RecyclerView, so I will have two sources of data but one Recycler, do I have to create also a MediatorLiveData? (I don't add any code but if it help I can do it)
One person asked how exactly I did it (Question posted as answer so it is deleted now but maybe it will help someone in future). So, in ViewModel I have this:
// this flow keeps query. If it is null it means that I want to get all News from API. If it is not null it means that I want to make another API request which takes a parameter query
private val _queryFlow: MutableStateFlow<String?> = MutableStateFlow(null)
val queryFlow: StateFlow<String?>
get() = _queryFlow
// this function set and validate query
fun submitQuery(query: String?)
{
Timber.d("Submit new search $query")
_queryFlow.value = when
{
query.isNullOrEmpty() -> null
query.trim()
.isNotBlank() -> query.trim()
else -> null
}
}
// flow of paging data that I am using in RecyclerView
@ExperimentalCoroutinesApi
val homeNewsData = _queryFlow.flatMapLatest {
searchNews(it)
}
private fun searchNews(
query: String?
): Flow<PagingData<NewsRecyclerModel>>
{
return newsRepository.getSearchResultStream(
query
)
// mapping, filtering, separators etc.
.cachedIn(viewModelScope)
}
NewsRepository has this function used in VM:
fun getSearchResultStream(searchKey: String?): Flow<PagingData<News>>
{
val pagingSourceFactory = { database.cacheNewsDao.getNews() }
return Pager(
config = PagingConfig(
pageSize = NETWORK_PAGE_SIZE,
enablePlaceholders = false,
initialLoadSize = INITIAL_LOAD_SIZE
),
remoteMediator = newsRemoteMediator.apply { this.searchKey = searchKey },
pagingSourceFactory = pagingSourceFactory
).flow
}
NewsRemoteMedietor:
// it keeps submitted query. based on this I can letter define which API request I want to do
var searchKey: String? = null
override suspend fun load(loadType: LoadType, state: PagingState<Int, News>): MediatorResult
{
\\ all logic the same like in codelabs
try
{
val apiResponse =
if (searchKey.isNullOrEmpty()) // query is null/empty get Trending news
newsRetrofit.getTrending(
state.config.pageSize,
page * state.config.pageSize
)
else // query is not blank, make API request with search keyword
newsRetrofit.getSearched(
state.config.pageSize,
page * state.config.pageSize,
searchKey!!
)
\\ again the same logic like in codelabs
}
}
I don't know if it is the best way to do it (probably not) but in my case, it was working