Combine search and sort with kotlin flow - kotlin

Question

I need to search and sort data simultaneously. I did it for search but it wont trigger for sort. I'm also using pagination.
User can type in searchView and flow will trigger, but problem is when i change sortState (ascending or descending) it wont trigger flow for searching articles on api endpoint.
ViewModel:
private val currentQuery = MutableStateFlow(DEFAULT_QUERY)
private val sortState = MutableStateFlow<SortOrderState>(SortOrderState.Ascending)
val flow = currentQuery
.debounce(2300)
.filter {
it.trim().isNotEmpty()
}
.distinctUntilChanged()
.flatMapLatest { query ->
articleRepository.getSearchResult(query.lowercase(Locale.ROOT),sortState.value)
}
Fragment:
lifecycleScope.launch {
viewModel.flow.collectLatest { articles ->
binding.recyclerViewTop.layoutManager = LinearLayoutManager(context)
binding.recyclerViewTop.adapter = adapter.withLoadStateHeaderAndFooter(
header = ArticleLoadStateAdapter { adapter.retry() },
footer = ArticleLoadStateAdapter { adapter.retry() }
)
adapter.submitData(articles)
}
}
In fragment I have function: viewModel.searchNews(newText)
And in Main activity: viewModel.setSortState(SortOrderState.Ascending) (one menu item clicked) to see if MutableStateFlow.value is changed. I can see that in ViewModel i can change these values but if I do:
val flow=currentQuery.combine(sortState){
query,state ->
}
I never changes if I click on sort menu item, only if I type something to search.
Edit: sortState is not updating in flow variable, I checked setSortState and I can clearly see that state is changed but in flow I only send ascending all the time.
Main activity:
override fun onOptionsItemSelected(item: MenuItem): Boolean {
when (item.itemId) {
R.id.menu_sortAsc -> {
viewModel.setSortState(SortOrderState.Ascending)
}
R.id.menu_sortDesc -> {
viewModel.setSortState(SortOrderState.Descening)
}
}
return super.onOptionsItemSelected(item)
}
ViewModel:
fun setSortState(sortOrderState: SortOrderState) {
sortState.value = sortOrderState
}
SortOrderState:
sealed interface SortOrderState{
object Ascending : SortOrderState
object Descening : SortOrderState
}
Edit 2: Collecting in HomeFragment it always gives me Ascending value even if i click on menu item for descending sort
lifecycleScope.launch {
viewModel.sortState.collectLatest {
Log.d(TAG, "onCreateViewSort: $it")
}
In ViewModel I can see sortState is changed:
fun setSortState(sortOrderState: SortOrderState) {
sortState.value = sortOrderState
Log.d(TAG, "setSortState: ${sortState.value}")
}

Answer 1

You aren't using your sort state as a Flow. You're only passively using its value, so your output flow won't automatically update when the value changes.
Instead, you need to combine your flows.
Here, I also moved your lowercase transformation before the distinctUntilChanged because I think that makes more logical sense. Also, it makes sense to include the trim in the transformation and not just in the filter.
val flow = currentQuery
.debounce(2300)
.map { it.trim().lowercase(Locale.ROOT) }
.filter { it.isNotEmpty() }
.distinctUntilChanged()
.combine(sortState) { query, sort -> query to sort }
.flatMapLatest { (query, sort) ->
articleRepository.getSearchResult(query, sort)
}
You might also consider tagging this with shareIn(viewModelScope, SharingStarted.WhileSubscribed(5000), 1) so the search doesn't have to restart on a screen rotation.