Hide reading fab if history is empty

app/src/main/java/org/koitharu/kotatsu/history/data/HistoryDao.kt

@@ -38,6 +38,9 @@ abstract class HistoryDao {
 	@Query("SELECT * FROM history WHERE manga_id = :id")
 	abstract fun observe(id: Long): Flow<HistoryEntity?>
 
+	@Query("SELECT COUNT(*) FROM history")
+	abstract fun observeCount(): Flow<Int>
+
 	@Query("DELETE FROM history")
 	abstract suspend fun clear()
 

app/src/main/java/org/koitharu/kotatsu/history/domain/HistoryRepository.kt

@@ -2,6 +2,7 @@ package org.koitharu.kotatsu.history.domain
 
 import androidx.room.withTransaction
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.map
 import org.koitharu.kotatsu.core.db.MangaDatabase
 import org.koitharu.kotatsu.core.db.entity.MangaEntity
@@ -26,6 +27,11 @@ class HistoryRepository(
 		return entities.map { it.manga.toManga(it.tags.mapToSet(TagEntity::toMangaTag)) }
 	}
 
+	suspend fun getLastOrNull(): Manga? {
+		val entity = db.historyDao.findAll(0, 1).firstOrNull() ?: return null
+		return entity.manga.toManga(entity.tags.mapToSet { it.toMangaTag() })
+	}
+
 	fun observeAll(): Flow<List<Manga>> {
 		return db.historyDao.observeAll().mapItems {
 			it.manga.toManga(it.tags.mapToSet(TagEntity::toMangaTag))
@@ -47,6 +53,12 @@ class HistoryRepository(
 		}
 	}
 
+	fun observeHasItems(): Flow<Boolean> {
+		return db.historyDao.observeCount()
+			.map { it > 0 }
+			.distinctUntilChanged()
+	}
+
 	suspend fun addOrUpdate(manga: Manga, chapterId: Long, page: Int, scroll: Int) {
 		if (manga.isNsfw && settings.isHistoryExcludeNsfw) {
 			return

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

@@ -11,16 +11,12 @@ import androidx.appcompat.app.ActionBarDrawerToggle
 import androidx.appcompat.view.ActionMode
 import androidx.core.content.ContextCompat
 import androidx.core.graphics.Insets
-import androidx.core.view.GravityCompat
+import androidx.core.view.*
-import androidx.core.view.ViewCompat
-import androidx.core.view.updateLayoutParams
-import androidx.core.view.updatePadding
 import androidx.drawerlayout.widget.DrawerLayout
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentTransaction
 import androidx.fragment.app.commit
 import androidx.lifecycle.lifecycleScope
-import androidx.swiperefreshlayout.widget.CircularProgressDrawable
 import com.google.android.material.appbar.AppBarLayout
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.navigation.NavigationView
@@ -135,6 +131,7 @@ class MainActivity :
 		viewModel.onOpenReader.observe(this, this::onOpenReader)
 		viewModel.onError.observe(this, this::onError)
 		viewModel.isLoading.observe(this, this::onLoadingStateChanged)
+		viewModel.isResumeEnabled.observe(this, this::onResumeEnabledChanged)
 		viewModel.remoteSources.observe(this, this::updateSideMenu)
 		viewModel.isSuggestionsEnabled.observe(this, this::setSuggestionsEnabled)
 	}
@@ -313,14 +310,17 @@ class MainActivity :
 	}
 
 	private fun onError(e: Throwable) {
-		Snackbar.make(binding.container, e.getDisplayMessage(resources), Snackbar.LENGTH_SHORT)
+		Snackbar.make(binding.container, e.getDisplayMessage(resources), Snackbar.LENGTH_SHORT).show()
-			.show()
 	}
 
 	private fun onLoadingStateChanged(isLoading: Boolean) {
 		binding.fab.isEnabled = !isLoading
 	}
 
+	private fun onResumeEnabledChanged(isEnabled: Boolean) {
+		adjustFabVisibility(isResumeEnabled = isEnabled)
+	}
+
 	private fun updateSideMenu(remoteSources: List<MangaSource>) {
 		val submenu = binding.navigationView.menu.findItem(R.id.nav_remote_sources).subMenu
 		submenu.removeGroup(R.id.group_remote_sources)
@@ -397,10 +397,20 @@ class MainActivity :
 	}
 
 	private fun adjustFabVisibility(
+		isResumeEnabled: Boolean = viewModel.isResumeEnabled.value == true,
 		topFragment: Fragment? = supportFragmentManager.findFragmentByTag(TAG_PRIMARY),
 		isSearchOpened: Boolean = supportFragmentManager.findFragmentByTag(TAG_SEARCH)?.isVisible == true,
 	) {
-		if (!isSearchOpened && topFragment is HistoryListFragment) binding.fab.show() else binding.fab.hide()
+		val fab = binding.fab
+		if (isResumeEnabled && !isSearchOpened && topFragment is HistoryListFragment) {
+			if (!fab.isVisible) {
+				fab.show()
+			}
+		} else {
+			if (fab.isVisible) {
+				fab.hide()
+			}
+		}
 	}
 
 	private fun adjustDrawerLock() {

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

@@ -27,6 +27,10 @@ class MainViewModel(
 		.map { settings.isSuggestionsEnabled }
 		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
 
+	val isResumeEnabled = historyRepository
+		.observeHasItems()
+		.asLiveDataDistinct(viewModelScope.coroutineContext + Dispatchers.Default)
+
 	val remoteSources = settings.observe()
 		.filter { it == AppSettings.KEY_SOURCES_ORDER || it == AppSettings.KEY_SOURCES_HIDDEN }
 		.onStart { emit("") }
@@ -35,9 +39,8 @@ class MainViewModel(
 
 	fun openLastReader() {
 		launchLoadingJob {
-			val manga = historyRepository.getList(0, 1).firstOrNull()
+			val manga = historyRepository.getLastOrNull() ?: throw EmptyHistoryException()
-				?: throw EmptyHistoryException()
 			onOpenReader.call(manga)
 		}
 	}
-}
+}