Loading indicator does not hide if api failed to retrieve data although it hides if api succeed to retrieve data in Android Paging library - retrofit2

Question

I have a remote server from where I want to fetch 20 items(Job) per api call and show them in RecyclerView using paging library.
For that, I want to show a loading indicator at the beginning of the first api call when list of items is being fetched from the server. Everything is okay if data is fetched successfully. That means the loading indicator got invisible if data loaded successfully. The code is given bellow.
JobService.KT
#GET(Constants.API_JOB_LIST)
fun getJobPost(
#Query("page") pageNumber: Int
): Observable<Response<JobResponse>>
JobResponse.kt
data class JobResponse(
#SerializedName("status") val status: Int? = null,
#SerializedName("message") val message: Any? = null,
#SerializedName("data") val jobData: JobData? = null
)
JobData.kt
data class JobData(
#SerializedName("jobs") val jobs: List<Job?>? = null,
#SerializedName("total") val totalJob: Int? = null,
#SerializedName("page") val currentPage: Int? = null,
#SerializedName("showing") val currentlyShowing: Int? = null,
#SerializedName("has_more") val hasMore: Boolean? = null
)
NetworkState.kt
sealed class NetworkState {
data class Progress(val isLoading: Boolean) : NetworkState()
data class Failure(val errorMessage: String?) : NetworkState()
companion object {
fun loading(isLoading: Boolean): NetworkState = Progress(isLoading)
fun failure(errorMessage: String?): NetworkState = Failure(errorMessage)
}
}
Event.kt
open class Event<out T>(private val content: T) {
private var hasBeenHandled = false
fun getContentIfNotHandled() = if (hasBeenHandled) {
null
} else {
hasBeenHandled = true
content
}
fun peekContent() = content
}
JobDataSource.kt
class JobDataSource(
private val jobService: JobService,
private val compositeDisposable: CompositeDisposable
) : PageKeyedDataSource<Int, Job>() {
val paginationState: MutableLiveData<Event<NetworkState>> = MutableLiveData()
val initialLoadingState: MutableLiveData<Event<NetworkState>> = MutableLiveData()
val totalJob: MutableLiveData<Event<Int>> = MutableLiveData()
companion object {
private const val FIRST_PAGE = 1
}
override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, Job>) {
compositeDisposable += jobService.getJobPost(FIRST_PAGE)
.performOnBackgroundOutputOnMain()
.doOnSubscribe { initialLoadingState.postValue(Event(loading(true))) }
.doOnTerminate { initialLoadingState.postValue(Event(loading(false))) }
.subscribe({
if (it.isSuccessful) {
val jobData = it.body()?.jobData
totalJob.postValue(Event(jobData?.totalJob!!))
jobData.jobs?.let { jobs -> callback.onResult(jobs, null, FIRST_PAGE+1) }
} else {
val error = Gson().fromJson(it.errorBody()?.charStream(), ApiError::class.java)
when (it.code()) {
CUSTOM_STATUS_CODE -> initialLoadingState.postValue(Event(failure(error.message!!)))
else -> initialLoadingState.postValue(Event(failure("Something went wrong")))
}
}
}, {
if (it is IOException) {
initialLoadingState.postValue(Event(failure("Check Internet Connectivity")))
} else {
initialLoadingState.postValue(Event(failure("Json Parsing error")))
}
})
}
override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, Job>) {
compositeDisposable += jobService.getJobPost(params.key)
.performOnBackgroundOutputOnMain()
.doOnSubscribe { if (params.key != 2) paginationState.postValue(Event(loading(true))) }
.doOnTerminate { paginationState.postValue(Event(loading(false))) }
.subscribe({
if (it.isSuccessful) {
val jobData = it.body()?.jobData
totalJob.postValue(Event(jobData?.totalJob!!))
jobData.jobs?.let { jobs -> callback.onResult(jobs, if (jobData.hasMore!!) params.key+1 else null) }
} else {
val error = Gson().fromJson(it.errorBody()?.charStream(), ApiError::class.java)
when (it.code()) {
CUSTOM_STATUS_CODE -> initialLoadingState.postValue(Event(failure(error.message!!)))
else -> initialLoadingState.postValue(Event(failure("Something went wrong")))
}
}
}, {
if (it is IOException) {
paginationState.postValue(Event(failure("Check Internet Connectivity")))
} else {
paginationState.postValue(Event(failure("Json Parsing error")))
}
})
}
override fun loadBefore(params: LoadParams<Int>, callback: LoadCallback<Int, Job>) {}
}
JobDataSourceFactory.kt
class JobDataSourceFactory(
private val jobService: JobService,
private val compositeDisposable: CompositeDisposable
): DataSource.Factory<Int, Job>() {
val jobDataSourceLiveData = MutableLiveData<JobDataSource>()
override fun create(): DataSource<Int, Job> {
val jobDataSource = JobDataSource(jobService, compositeDisposable)
jobDataSourceLiveData.postValue(jobDataSource)
return jobDataSource
}
}
JobBoardViewModel.kt
class JobBoardViewModel(
private val jobService: JobService
) : BaseViewModel() {
companion object {
private const val PAGE_SIZE = 20
private const val PREFETCH_DISTANCE = 20
}
private val jobDataSourceFactory: JobDataSourceFactory = JobDataSourceFactory(jobService, compositeDisposable)
var jobList: LiveData<PagedList<Job>>
init {
val config = PagedList.Config.Builder()
.setPageSize(PAGE_SIZE)
.setInitialLoadSizeHint(PAGE_SIZE)
.setPrefetchDistance(PREFETCH_DISTANCE)
.setEnablePlaceholders(false)
.build()
jobList = LivePagedListBuilder(jobDataSourceFactory, config).build()
}
fun getPaginationState(): LiveData<Event<NetworkState>> = Transformations.switchMap<JobDataSource, Event<NetworkState>>(
jobDataSourceFactory.jobDataSourceLiveData,
JobDataSource::paginationState
)
fun getInitialLoadingState(): LiveData<Event<NetworkState>> = Transformations.switchMap<JobDataSource, Event<NetworkState>>(
jobDataSourceFactory.jobDataSourceLiveData,
JobDataSource::initialLoadingState
)
fun getTotalJob(): LiveData<Event<Int>> = Transformations.switchMap<JobDataSource, Event<Int>>(
jobDataSourceFactory.jobDataSourceLiveData,
JobDataSource::totalJob
)
}
JobBoardFragment.kt
class JobBoardFragment : BaseFragment() {
private val viewModel: JobBoardViewModel by lazy {
getViewModel { JobBoardViewModel(ApiFactory.jobListApi) }
}
private val jobAdapter by lazy {
JobAdapter {
val bundle = Bundle()
bundle.putInt(CLICKED_JOB_ID, it.jobId!!)
navigateTo(R.id.jobBoard_to_jobView, R.id.home_navigation_fragment, bundle)
}
}
override fun getLayoutResId() = R.layout.fragment_job_board
override fun initWidget() {
job_list_recycler_view.adapter = jobAdapter
back_to_main_image_view.setOnClickListener { onBackPressed() }
}
override fun observeLiveData() {
with(viewModel) {
jobList.observe(this#JobBoardFragment, Observer {
jobAdapter.submitList(it)
})
getInitialLoadingState().observe(this#JobBoardFragment, Observer {
it.getContentIfNotHandled()?.let { state ->
when (state) {
is Progress -> {
if (state == loading(true)) {
network_loading_indicator.visible()
} else {
network_loading_indicator.visibilityGone()
}
}
is Failure -> context?.showToast(state.errorMessage.toString())
}
}
})
getPaginationState().observe(this#JobBoardFragment, Observer {
it.getContentIfNotHandled()?.let { state ->
when (state) {
is Progress -> {
if (state == loading(true)) {
pagination_loading_indicator.visible()
} else {
pagination_loading_indicator.visibilityGone()
}
}
is Failure -> context?.showToast(state.errorMessage.toString())
}
}
})
getTotalJob().observe(this#JobBoardFragment, Observer {
it.getContentIfNotHandled()?.let { state ->
job_board_text_view.visible()
with(profile_completed_image_view) {
visible()
text = state.toString()
}
}
})
}
}
}
But the problem is if data fetching failed due to internet connectivity or any other server related problem loading indicator does not invisible that means it still loading though I make the loadingStatus false and error message is shown. it means .doOnTerminate { initialLoadingState.postValue(Event(loading(false))) } is not called if error occured. This is the first problem. Another problem is loadInitial() and loadAfter() is being called simultaneously at the first call. But I just want the loadInitial() method is called at the beginning. after scrolling loadAfter() method will be called.

Answer 1

Try replacing all your LiveData's postValue() methods by setValue() or simply .value =.
The problem is that the postValue() method is for updating the value from a background thread to observers in the main thread. In this case you are always changing the values from the main thread itself, so you should use .value =.
Hope it's not too late.