Optimize LiveData from flows

app/build.gradle

@@ -101,7 +101,7 @@ dependencies {
 	implementation 'com.davemorrissey.labs:subsampling-scale-image-view-androidx:3.10.0'
 	implementation 'com.tomclaw.cache:cache:1.0'
 
-	debugImplementation 'com.squareup.leakcanary:leakcanary-android:2.5'
+	debugImplementation 'com.squareup.leakcanary:leakcanary-android:2.6'
 
 	testImplementation 'junit:junit:4.13.1'
 	testImplementation 'org.json:json:20201115'

app/src/main/java/org/koitharu/kotatsu/details/ui/DetailsViewModel.kt

@@ -77,7 +77,7 @@ class DetailsViewModel(
 				}
 			)
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
+	}.asLiveData(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	init {
 		launchLoadingJob(Dispatchers.Default) {

app/src/main/java/org/koitharu/kotatsu/favourites/ui/FavouritesContainerFragment.kt

@@ -1,7 +1,6 @@
 package org.koitharu.kotatsu.favourites.ui
 
 import android.os.Bundle
-import android.os.Parcelable
 import android.view.*
 import androidx.core.graphics.Insets
 import androidx.core.view.updatePadding
@@ -27,7 +26,6 @@ class FavouritesContainerFragment : BaseFragment<FragmentFavouritesBinding>(),
 	private val editDelegate by lazy(LazyThreadSafetyMode.NONE) {
 		CategoriesEditDelegate(requireContext(), this)
 	}
-	private var adapterState: Parcelable? = null
 
 	override fun onCreate(savedInstanceState: Bundle?) {
 		super.onCreate(savedInstanceState)
@@ -49,25 +47,6 @@ class FavouritesContainerFragment : BaseFragment<FragmentFavouritesBinding>(),
 		viewModel.onError.observe(viewLifecycleOwner, ::onError)
 	}
 
-	override fun onViewStateRestored(savedInstanceState: Bundle?) {
-		super.onViewStateRestored(savedInstanceState)
-		// (savedInstanceState?.getParcelable(KEY_ADAPTER_STATE) ?: adapterState)?.let {
-		// 	(binding.pager.adapter as FavouritesPagerAdapter).restoreState(it)
-		// }
-	}
-
-	override fun onDestroyView() {
-		adapterState = (binding.pager.adapter as? FavouritesPagerAdapter)?.saveState()
-		super.onDestroyView()
-	}
-
-	override fun onSaveInstanceState(outState: Bundle) {
-		super.onSaveInstanceState(outState)
-		adapterState = (bindingOrNull()?.pager?.adapter as? FavouritesPagerAdapter)?.saveState()
-			?: adapterState
-		outState.putParcelable(KEY_ADAPTER_STATE, adapterState)
-	}
-
 	override fun onWindowInsetsChanged(insets: Insets) {
 		binding.tabs.updatePadding(
 			left = insets.left,
@@ -132,8 +111,6 @@ class FavouritesContainerFragment : BaseFragment<FragmentFavouritesBinding>(),
 
 	companion object {
 
-		private const val KEY_ADAPTER_STATE = "adapter_state"
-
 		fun newInstance() = FavouritesContainerFragment()
 	}
 }

app/src/main/java/org/koitharu/kotatsu/favourites/ui/categories/FavouritesCategoriesViewModel.kt

@@ -1,12 +1,11 @@
 package org.koitharu.kotatsu.favourites.ui.categories
 
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.favourites.domain.FavouritesRepository
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 
 class FavouritesCategoriesViewModel(
 	private val repository: FavouritesRepository
@@ -15,7 +14,7 @@ class FavouritesCategoriesViewModel(
 	private var reorderJob: Job? = null
 
 	val categories = repository.observeCategories()
-		.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
+		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	fun createCategory(name: String) {
 		launchJob(Dispatchers.Default) {

app/src/main/java/org/koitharu/kotatsu/favourites/ui/categories/select/MangaCategoriesViewModel.kt

@@ -1,14 +1,13 @@
 package org.koitharu.kotatsu.favourites.ui.categories.select
 
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.core.model.Manga
 import org.koitharu.kotatsu.favourites.domain.FavouritesRepository
 import org.koitharu.kotatsu.favourites.ui.categories.select.model.MangaCategoryItem
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 
 class MangaCategoriesViewModel(
 	private val manga: Manga,
@@ -26,7 +25,7 @@ class MangaCategoriesViewModel(
 				isChecked = it.id in checked
 			)
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	fun setChecked(categoryId: Long, isChecked: Boolean) {
 		launchJob(Dispatchers.Default) {

app/src/main/java/org/koitharu/kotatsu/favourites/ui/list/FavouritesListViewModel.kt

@@ -4,7 +4,6 @@ import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.model.Manga
 import org.koitharu.kotatsu.core.prefs.AppSettings
@@ -14,7 +13,7 @@ import org.koitharu.kotatsu.list.ui.model.EmptyState
 import org.koitharu.kotatsu.list.ui.model.LoadingState
 import org.koitharu.kotatsu.list.ui.model.toErrorState
 import org.koitharu.kotatsu.list.ui.model.toUi
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.utils.ext.onFirst
 
 class FavouritesListViewModel(
@@ -43,7 +42,7 @@ class FavouritesListViewModel(
 		isLoading.postValue(false)
 	}.catch {
 		emit(listOf(it.toErrorState(canRetry = false)))
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	override fun onRefresh() = Unit
 

app/src/main/java/org/koitharu/kotatsu/history/ui/HistoryListViewModel.kt

@@ -15,7 +15,7 @@ import org.koitharu.kotatsu.history.domain.MangaWithHistory
 import org.koitharu.kotatsu.list.ui.MangaListViewModel
 import org.koitharu.kotatsu.list.ui.model.*
 import org.koitharu.kotatsu.utils.SingleLiveEvent
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.utils.ext.daysDiff
 import org.koitharu.kotatsu.utils.ext.onFirst
 import java.util.*
@@ -51,7 +51,7 @@ class HistoryListViewModel(
 		isLoading.postValue(false)
 	}.catch {
 		it.toErrorState(canRetry = false)
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	override fun onRefresh() = Unit
 

app/src/main/java/org/koitharu/kotatsu/list/ui/MangaListFragment.kt

@@ -50,6 +50,9 @@ abstract class MangaListFragment : BaseFragment<FragmentListBinding>(),
 	private var paginationListener: PaginationScrollListener? = null
 	private val spanResolver = MangaListSpanResolver()
 	private val spanSizeLookup = SpanSizeLookup()
+	private val listCommitCallback = Runnable {
+		spanSizeLookup.invalidateCache()
+	}
 	open val isSwipeRefreshEnabled = true
 
 	protected abstract val viewModel: MangaListViewModel
@@ -148,8 +151,7 @@ abstract class MangaListFragment : BaseFragment<FragmentListBinding>(),
 	}
 
 	private fun onListChanged(list: List<ListModel>) {
-		spanSizeLookup.invalidateCache()
+		listAdapter?.setItems(list, listCommitCallback)
-		listAdapter?.items = list
 	}
 
 	private fun onError(e: Throwable) {
@@ -178,7 +180,7 @@ abstract class MangaListFragment : BaseFragment<FragmentListBinding>(),
 
 	@CallSuper
 	protected open fun onLoadingStateChanged(isLoading: Boolean) {
-		binding.swipeRefreshLayout.isEnabled =
+		binding.swipeRefreshLayout.isEnabled = binding.swipeRefreshLayout.isRefreshing ||
 			isSwipeRefreshEnabled && !isLoading
 		if (!isLoading) {
 			binding.swipeRefreshLayout.isRefreshing = false

app/src/main/java/org/koitharu/kotatsu/list/ui/MangaListViewModel.kt

@@ -2,7 +2,6 @@ package org.koitharu.kotatsu.list.ui
 
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.*
@@ -10,6 +9,7 @@ import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.core.prefs.ListMode
 import org.koitharu.kotatsu.list.ui.model.ListModel
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 
 abstract class MangaListViewModel(
 	private val settings: AppSettings
@@ -21,16 +21,20 @@ abstract class MangaListViewModel(
 	val gridScale = settings.observe()
 		.filter { it == AppSettings.KEY_GRID_SIZE }
 		.map { settings.gridSize / 100f }
-		.onStart { emit(settings.gridSize / 100f) }
+		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.IO) {
-		.flowOn(Dispatchers.IO)
+			settings.gridSize / 100f
-		.asLiveData(viewModelScope.coroutineContext)
+		}
 
 	protected fun createListModeFlow() = settings.observe()
 		.filter { it == AppSettings.KEY_LIST_MODE }
 		.map { settings.listMode }
 		.onStart { emit(settings.listMode) }
 		.distinctUntilChanged()
-		.onEach { listMode.postValue(it) }
+		.onEach {
+			if (listMode.value != it) {
+				listMode.postValue(it)
+			}
+		}
 
 	abstract fun onRefresh()
 

app/src/main/java/org/koitharu/kotatsu/list/ui/adapter/MangaListAdapter.kt

@@ -6,6 +6,7 @@ import coil.ImageLoader
 import com.hannesdorfmann.adapterdelegates4.AsyncListDifferDelegationAdapter
 import org.koitharu.kotatsu.base.ui.list.OnListItemClickListener
 import org.koitharu.kotatsu.core.model.Manga
+import org.koitharu.kotatsu.core.ui.DateTimeAgo
 import org.koitharu.kotatsu.list.ui.model.ListModel
 import org.koitharu.kotatsu.list.ui.model.MangaGridModel
 import org.koitharu.kotatsu.list.ui.model.MangaListDetailedModel
@@ -38,6 +39,10 @@ class MangaListAdapter(
 			.addDelegate(ITEM_TYPE_EMPTY, emptyStateListAD())
 	}
 
+	fun setItems(list: List<ListModel>, commitCallback: Runnable) {
+		differ.submitList(list, commitCallback)
+	}
+
 	private class DiffCallback : DiffUtil.ItemCallback<ListModel>() {
 
 		override fun areItemsTheSame(oldItem: ListModel, newItem: ListModel) = when {
@@ -50,6 +55,9 @@ class MangaListAdapter(
 			oldItem is MangaGridModel && newItem is MangaGridModel -> {
 				oldItem.id == newItem.id
 			}
+			oldItem is DateTimeAgo && newItem is DateTimeAgo -> {
+				oldItem == newItem
+			}
 			else -> oldItem.javaClass == newItem.javaClass
 		}
 

app/src/main/java/org/koitharu/kotatsu/local/ui/LocalListViewModel.kt

@@ -2,13 +2,10 @@ package org.koitharu.kotatsu.local.ui
 
 import android.content.Context
 import android.net.Uri
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
-import kotlinx.coroutines.flow.onStart
 import kotlinx.coroutines.withContext
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.exceptions.UnsupportedFileException
@@ -24,6 +21,7 @@ import org.koitharu.kotatsu.list.ui.model.toUi
 import org.koitharu.kotatsu.local.domain.LocalMangaRepository
 import org.koitharu.kotatsu.utils.MediaStoreCompat
 import org.koitharu.kotatsu.utils.SingleLiveEvent
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.utils.ext.safe
 import org.koitharu.kotatsu.utils.ext.sub
 import java.io.IOException
@@ -51,9 +49,7 @@ class LocalListViewModel(
 			list.isEmpty() -> listOf(EmptyState(R.string.text_local_holder))
 			else -> list.toUi(mode)
 		}
-	}.onStart {
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
-		emit(listOf(LoadingState))
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
 
 	init {
 		onRefresh()

app/src/main/java/org/koitharu/kotatsu/main/ui/MainViewModel.kt

@@ -1,9 +1,10 @@
 package org.koitharu.kotatsu.main.ui
 
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.flow.filter
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onStart
 import org.koitharu.kotatsu.base.domain.MangaProviderFactory
 import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.core.exceptions.EmptyHistoryException
@@ -11,6 +12,7 @@ import org.koitharu.kotatsu.core.model.Manga
 import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.history.domain.HistoryRepository
 import org.koitharu.kotatsu.utils.SingleLiveEvent
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 
 class MainViewModel(
 	private val historyRepository: HistoryRepository,
@@ -24,9 +26,7 @@ class MainViewModel(
 		.filter { it == AppSettings.KEY_SOURCES_ORDER || it == AppSettings.KEY_SOURCES_HIDDEN }
 		.onStart { emit("") }
 		.map { MangaProviderFactory.getSources(settings, includeHidden = false) }
-		.distinctUntilChanged()
+		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
-		.flowOn(Dispatchers.Default)
-		.asLiveData(viewModelScope.coroutineContext)
 
 	fun openLastReader() {
 		launchLoadingJob {

app/src/main/java/org/koitharu/kotatsu/reader/ui/ReaderViewModel.kt

@@ -5,7 +5,6 @@ import android.net.Uri
 import android.util.LongSparseArray
 import android.webkit.URLUtil
 import androidx.lifecycle.MutableLiveData
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.*
 import kotlinx.coroutines.flow.*
@@ -58,7 +57,7 @@ class ReaderViewModel(
 			chapterNumber = chapter?.number ?: 0,
 			chaptersTotal = chapters.size()
 		)
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	val content = MutableLiveData<ReaderContent>(ReaderContent(emptyList(), null))
 	val manga: Manga?
@@ -68,9 +67,7 @@ class ReaderViewModel(
 		.filter { it == AppSettings.KEY_READER_ANIMATION }
 		.map { settings.readerAnimation }
 		.onStart { emit(settings.readerAnimation) }
-		.distinctUntilChanged()
+		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.IO)
-		.flowOn(Dispatchers.IO)
-		.asLiveData(viewModelScope.coroutineContext)
 
 	val onZoomChanged = SingleLiveEvent<Unit>()
 

app/src/main/java/org/koitharu/kotatsu/remotelist/ui/RemoteListViewModel.kt

@@ -5,7 +5,6 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.model.Manga
@@ -15,7 +14,7 @@ import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.list.ui.MangaFilterConfig
 import org.koitharu.kotatsu.list.ui.MangaListViewModel
 import org.koitharu.kotatsu.list.ui.model.*
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import java.util.*
 
 class RemoteListViewModel(
@@ -49,7 +48,7 @@ class RemoteListViewModel(
 				result
 			}
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	init {
 		loadList(false)

app/src/main/java/org/koitharu/kotatsu/search/ui/SearchViewModel.kt

@@ -5,14 +5,13 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.model.Manga
 import org.koitharu.kotatsu.core.parser.MangaRepository
 import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.list.ui.MangaListViewModel
 import org.koitharu.kotatsu.list.ui.model.*
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import java.util.*
 
 class SearchViewModel(
@@ -46,7 +45,7 @@ class SearchViewModel(
 				result
 			}
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	init {
 		loadList(append = false)

app/src/main/java/org/koitharu/kotatsu/search/ui/global/GlobalSearchViewModel.kt

@@ -11,7 +11,7 @@ import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.list.ui.MangaListViewModel
 import org.koitharu.kotatsu.list.ui.model.*
 import org.koitharu.kotatsu.search.domain.MangaSearchRepository
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.utils.ext.onFirst
 import java.util.*
 
@@ -46,7 +46,7 @@ class GlobalSearchViewModel(
 				result
 			}
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	init {
 		onRefresh()

app/src/main/java/org/koitharu/kotatsu/tracker/ui/FeedViewModel.kt

@@ -8,7 +8,6 @@ import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.filterNotNull
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.core.model.TrackingLogItem
@@ -17,7 +16,7 @@ import org.koitharu.kotatsu.list.ui.model.LoadingFooter
 import org.koitharu.kotatsu.list.ui.model.LoadingState
 import org.koitharu.kotatsu.tracker.domain.TrackingRepository
 import org.koitharu.kotatsu.tracker.ui.model.toFeedItem
-import org.koitharu.kotatsu.utils.ext.asLiveData
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.utils.ext.mapItems
 
 class FeedViewModel(
@@ -41,7 +40,7 @@ class FeedViewModel(
 			isHasNextPage -> list + LoadingFooter
 			else -> list
 		}
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext, listOf(LoadingState))
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default, listOf(LoadingState))
 
 	init {
 		loadList(append = false)

app/src/main/java/org/koitharu/kotatsu/utils/ext/LiveDataExt.kt

@@ -26,14 +26,40 @@ fun <T> LiveData<T>.observeWithPrevious(owner: LifecycleOwner, observer: Buffere
 	}
 }
 
-fun <T> Flow<T>.asLiveData(
+fun <T> Flow<T>.asLiveDataDistinct(
+	context: CoroutineContext = EmptyCoroutineContext
+): LiveData<T> = liveData(context) {
+	collect {
+		if (it != latestValue) {
+			emit(it)
+		}
+	}
+}
+
+fun <T> Flow<T>.asLiveDataDistinct(
 	context: CoroutineContext = EmptyCoroutineContext,
 	defaultValue: T
-): LiveData<T> = liveData(context) {
+): LiveData<T> = liveData(context, 0L) {
 	if (latestValue == null) {
 		emit(defaultValue)
 	}
 	collect {
+		if (it != latestValue) {
 			emit(it)
 		}
+	}
+}
+
+fun <T> Flow<T>.asLiveDataDistinct(
+	context: CoroutineContext = EmptyCoroutineContext,
+	defaultValue: suspend () -> T
+): LiveData<T> = liveData(context) {
+	if (latestValue == null) {
+		emit(defaultValue())
+	}
+	collect {
+		if (it != latestValue) {
+			emit(it)
+		}
+	}
 }

app/src/main/java/org/koitharu/kotatsu/widget/shelf/ShelfConfigViewModel.kt

@@ -1,13 +1,12 @@
 package org.koitharu.kotatsu.widget.shelf
 
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.flowOn
 import org.koitharu.kotatsu.base.ui.BaseViewModel
 import org.koitharu.kotatsu.favourites.domain.FavouritesRepository
+import org.koitharu.kotatsu.utils.ext.asLiveDataDistinct
 import org.koitharu.kotatsu.widget.shelf.model.CategoryItem
 import java.util.*
 
@@ -27,7 +26,7 @@ class ShelfConfigViewModel(
 			CategoryItem(it.id, it.title, selectedId == it.id)
 		}
 		list
-	}.flowOn(Dispatchers.Default).asLiveData(viewModelScope.coroutineContext)
+	}.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
 	var checkedId: Long by selectedCategoryId::value
 }