State flow for unit selection screens

app/src/main/java/com/sadellie/unitto/screens/second/SecondScreen.kt

@@ -45,6 +45,7 @@ import androidx.compose.ui.input.nestedscroll.nestedScroll
 import androidx.compose.ui.platform.LocalFocusManager
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.sadellie.unitto.R
 import com.sadellie.unitto.data.units.AbstractUnit
 import com.sadellie.unitto.data.units.UnitGroup
@@ -73,7 +74,7 @@ fun LeftSideScreen(
     navigateToSettingsActtion: () -> Unit,
     selectAction: (AbstractUnit) -> Unit
 ) {
-    val uiState = viewModel.uiState
+    val uiState = viewModel.mainFlow.collectAsStateWithLifecycle()
     val scrollBehavior = TopAppBarDefaults.pinnedScrollBehavior(rememberTopAppBarState())
     val chipsRowLazyListState = rememberLazyListState()
     val focusManager = LocalFocusManager.current
@@ -96,12 +97,12 @@ fun LeftSideScreen(
             ) {
                 SearchBar(
                     title = stringResource(R.string.units_screen_from),
-                    value = uiState.searchQuery,
+                    value = uiState.value.searchQuery,
                     onValueChange = {
                         viewModel.onSearchQueryChange(it)
                         viewModel.loadUnitsToShow(true)
                     },
-                    favoritesOnly = uiState.favoritesOnly,
+                    favoritesOnly = uiState.value.favoritesOnly,
                     favoriteAction = {
                         viewModel.toggleFavoritesOnly()
                         viewModel.loadUnitsToShow(true)
@@ -111,8 +112,8 @@ fun LeftSideScreen(
                     scrollBehavior = scrollBehavior
                 )
                 ChipsRow(
-                    chosenUnitGroup = viewModel.uiState.chosenUnitGroup,
-                    items = uiState.shownUnitGroups,
+                    chosenUnitGroup = uiState.value.chosenUnitGroup,
+                    items = uiState.value.shownUnitGroups,
                     selectAction = {
                         viewModel.toggleSelectedChip(it)
                         viewModel.loadUnitsToShow(true)
@@ -124,14 +125,14 @@ fun LeftSideScreen(
         }
     ) { paddingValues ->
         Crossfade(
-            targetState = uiState.unitsToShow.isEmpty(),
+            targetState = uiState.value.unitsToShow.isEmpty(),
             modifier = Modifier.padding(paddingValues)
         ) { noUnits ->
             if (noUnits) {
                 SearchPlaceholder(navigateToSettingsActtion = navigateToSettingsActtion)
             } else {
                 LazyColumn(Modifier.fillMaxSize()) {
-                    uiState.unitsToShow.forEach { (unitGroup, listOfUnits) ->
+                    uiState.value.unitsToShow.forEach { (unitGroup, listOfUnits) ->
                         item(unitGroup.name) {
                             UnitGroupHeader(Modifier.animateItemPlacement(), unitGroup)
                         }
@@ -163,7 +164,7 @@ fun LeftSideScreen(
         viewModel.setSelectedChip(currentUnit.group)
         viewModel.loadUnitsToShow(true)
 
-        val groupToSelect = uiState.shownUnitGroups.indexOf(currentUnit.group)
+        val groupToSelect = uiState.value.shownUnitGroups.indexOf(currentUnit.group)
         if (groupToSelect > -1) {
             chipsRowLazyListState.animateScrollToItem(groupToSelect)
         }
@@ -191,7 +192,7 @@ fun RightSideScreen(
     inputValue: BigDecimal,
     unitFrom: AbstractUnit
 ) {
-    val uiState = viewModel.uiState
+    val uiState = viewModel.mainFlow.collectAsStateWithLifecycle()
     val scrollBehavior = TopAppBarDefaults.pinnedScrollBehavior(rememberTopAppBarState())
     val focusManager = LocalFocusManager.current
 
@@ -200,12 +201,12 @@ fun RightSideScreen(
         topBar = {
             SearchBar(
                 title = stringResource(R.string.units_screen_from),
-                value = uiState.searchQuery,
+                value = uiState.value.searchQuery,
                 onValueChange = {
                     viewModel.onSearchQueryChange(it)
                     viewModel.loadUnitsToShow(false)
                 },
-                favoritesOnly = uiState.favoritesOnly,
+                favoritesOnly = uiState.value.favoritesOnly,
                 favoriteAction = {
                     viewModel.toggleFavoritesOnly()
                     viewModel.loadUnitsToShow(false)
@@ -217,14 +218,14 @@ fun RightSideScreen(
         }
     ) { paddingValues ->
         Crossfade(
-            targetState = uiState.unitsToShow.isEmpty(),
+            targetState = uiState.value.unitsToShow.isEmpty(),
             modifier = Modifier.padding(paddingValues)
         ) { noUnits ->
             if (noUnits) {
                 SearchPlaceholder(navigateToSettingsActtion = navigateToSettingsActtion)
             } else {
                 LazyColumn(Modifier.fillMaxSize()) {
-                    uiState.unitsToShow.forEach { (unitGroup, listOfUnits) ->
+                    uiState.value.unitsToShow.forEach { (unitGroup, listOfUnits) ->
                         item(unitGroup.name) {
                             UnitGroupHeader(Modifier.animateItemPlacement(), unitGroup)
                         }

app/src/main/java/com/sadellie/unitto/screens/second/SecondViewModel.kt

@@ -18,9 +18,6 @@
 
 package com.sadellie.unitto.screens.second
 
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.setValue
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.sadellie.unitto.data.units.AbstractUnit
@@ -31,6 +28,10 @@ import com.sadellie.unitto.data.units.database.MyBasedUnit
 import com.sadellie.unitto.data.units.database.MyBasedUnitsRepository
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import javax.inject.Inject
@@ -39,18 +40,26 @@ import javax.inject.Inject
 class SecondViewModel @Inject constructor(
     private val basedUnitRepository: MyBasedUnitsRepository,
     private val allUnitsRepository: AllUnitsRepository,
-    private val unitGroupsRepository: UnitGroupsRepository
+    unitGroupsRepository: UnitGroupsRepository
 ) : ViewModel() {
 
-    var uiState: SecondScreenUIState by mutableStateOf(SecondScreenUIState())
-        private set
+    private val _uiStateFlow = MutableStateFlow(SecondScreenUIState())
+
+    val mainFlow = combine(_uiStateFlow, unitGroupsRepository.shownUnitGroups) { uiState, shown ->
+        return@combine uiState.copy(shownUnitGroups = shown)
+    }
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5000),
+            initialValue = SecondScreenUIState()
+        )
 
     fun toggleFavoritesOnly() {
-        uiState = uiState.copy(favoritesOnly = !uiState.favoritesOnly)
+        _uiStateFlow.value = _uiStateFlow.value.copy(favoritesOnly = !_uiStateFlow.value.favoritesOnly)
     }
 
     fun onSearchQueryChange(newValue: String) {
-        uiState = uiState.copy(searchQuery = newValue)
+        _uiStateFlow.value = _uiStateFlow.value.copy(searchQuery = newValue)
     }
 
     /**
@@ -59,7 +68,7 @@ class SecondViewModel @Inject constructor(
      * @param unitGroup Chip to change to.
      */
     fun setSelectedChip(unitGroup: UnitGroup) {
-        uiState = uiState.copy(chosenUnitGroup = unitGroup)
+        _uiStateFlow.value = _uiStateFlow.value.copy(chosenUnitGroup = unitGroup)
     }
 
     /**
@@ -71,8 +80,8 @@ class SecondViewModel @Inject constructor(
      * @param unitGroup [UnitGroup], currently selected chip.
      */
     fun toggleSelectedChip(unitGroup: UnitGroup) {
-        val newUnitGroup = if (uiState.chosenUnitGroup == unitGroup) null else unitGroup
-        uiState = uiState.copy(chosenUnitGroup = newUnitGroup)
+        val newUnitGroup = if (_uiStateFlow.value.chosenUnitGroup == unitGroup) null else unitGroup
+        _uiStateFlow.value = _uiStateFlow.value.copy(chosenUnitGroup = newUnitGroup)
     }
 
     /**
@@ -90,13 +99,13 @@ class SecondViewModel @Inject constructor(
             withContext(Dispatchers.Default) {
                 val unitsToShow = allUnitsRepository.filterUnits(
                     hideBrokenCurrencies = hideBrokenCurrencies,
-                    chosenUnitGroup = uiState.chosenUnitGroup,
-                    favoritesOnly = uiState.favoritesOnly,
-                    searchQuery = uiState.searchQuery,
-                    allUnitsGroups = uiState.shownUnitGroups
+                    chosenUnitGroup = _uiStateFlow.value.chosenUnitGroup,
+                    favoritesOnly = _uiStateFlow.value.favoritesOnly,
+                    searchQuery = _uiStateFlow.value.searchQuery,
+                    allUnitsGroups = _uiStateFlow.value.shownUnitGroups
                 )
 
-                uiState = uiState.copy(unitsToShow = unitsToShow)
+                _uiStateFlow.value = _uiStateFlow.value.copy(unitsToShow = unitsToShow)
             }
         }
     }
@@ -119,12 +128,4 @@ class SecondViewModel @Inject constructor(
             )
         }
     }
-
-    init {
-        viewModelScope.launch {
-            unitGroupsRepository.shownUnitGroups.collect {
-                uiState = uiState.copy(shownUnitGroups = it)
-            }
-        }
-    }
 }