Simplifications and updates

gradle/libs.versions.toml

@@ -8,7 +8,7 @@ junitVersion = "1.1.5"
 espressoCore = "3.5.1"
 kotlinxCollectionsImmutable = "0.3.6"
 kotlinxSerializationJson = "1.6.1"
-ktorClient = "2.3.5"
+ktorClient = "2.3.6"
 lifecycleRuntimeKtx = "2.6.2"
 activityCompose = "1.8.1"
 composeBom = "2023.10.01"

kruiser/src/main/java/de/gaw/kruiser/backstack/Backstack.kt

@@ -3,9 +3,16 @@ package de.gaw.kruiser.backstack
 import de.gaw.kruiser.destination.Destination
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.coroutines.flow.StateFlow
+import java.io.Serializable
+import java.util.UUID
 
-typealias ImmutableEntries = ImmutableList<Destination>
-typealias BackstackEntries = List<Destination>
+typealias ImmutableEntries = ImmutableList<BackstackEntry>
+typealias BackstackEntries = List<BackstackEntry>
+
+data class BackstackEntry(
+ val destination: Destination,
+ val id: String = UUID.randomUUID().toString(),
+) : Serializable
 
 interface Backstack {
  val entries: StateFlow<BackstackEntries>

kruiser/src/main/java/de/gaw/kruiser/backstack/BackstackModifiers.kt

@@ -2,15 +2,17 @@ package de.gaw.kruiser.backstack
 
 import de.gaw.kruiser.destination.Destination
 
-
 fun MutableBackstack.pop() = mutate { dropLast(1) }
 
 fun MutableBackstack.push(destination: Destination) = mutate { this + destination }
 
 fun MutableBackstack.pushAvoidDuplicates(destination: Destination) = mutate {
  val currentItem = lastOrNull()
  when {
- currentItem != destination -> this + destination
+ currentItem?.destination != destination -> this + destination
  else -> this
  }
-}
+}
+
+operator fun BackstackEntries.plus(destination: Destination) =
+ this + BackstackEntry(destination = destination)

kruiser/src/main/java/de/gaw/kruiser/backstack/ui/ScreenContent.kt

@@ -6,6 +6,7 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.saveable.SaveableStateHolder
 import androidx.lifecycle.viewmodel.compose.LocalViewModelStoreOwner
 import de.gaw.kruiser.backstack.Backstack
+import de.gaw.kruiser.backstack.BackstackEntry
 import de.gaw.kruiser.backstack.ui.util.LocalBackstack
 import de.gaw.kruiser.backstack.ui.util.LocalSaveableStateHolder
 import de.gaw.kruiser.destination.Destination
@@ -16,16 +17,15 @@ import de.gaw.kruiser.viewmodel.viewModelStoreOwner
  */
 @Composable
 fun ScreenContent(
- destination: Destination,
- savedStateKey: Any = destination,
+ backstackEntry: BackstackEntry,
  stateHolder: SaveableStateHolder = LocalSaveableStateHolder.current,
  backstack: Backstack = LocalBackstack.current,
 ) {
- stateHolder.SaveableStateProvider(savedStateKey) {
- val destinationViewModelStoreOwner = backstack.viewModelStoreOwner(destination)
+ stateHolder.SaveableStateProvider(backstackEntry.id) {
+ val screen = remember(backstackEntry) { backstackEntry.destination.build() }
+ val destinationViewModelStoreOwner = backstack.viewModelStoreOwner(backstackEntry)
 
  CompositionLocalProvider(LocalViewModelStoreOwner provides destinationViewModelStoreOwner) {
- val screen = remember(destination) { destination.build() }
  screen.Content()
  }
  }

kruiser/src/main/java/de/gaw/kruiser/backstack/ui/animation/NoAnimation.kt

@@ -16,6 +16,6 @@ fun NoAnimation(
 ) {
  val entriesState = backstack.collectEntries()
  val entries by entriesState
- val currentEntry = entries.last()
- ScreenContent(currentEntry)
+ val entry = entries.last()
+ ScreenContent(entry)
 }

kruiser/src/main/java/de/gaw/kruiser/backstack/ui/animation/ScreenAnimation.kt

@@ -10,10 +10,10 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
 import de.gaw.kruiser.backstack.Backstack
 import de.gaw.kruiser.backstack.BackstackEntries
+import de.gaw.kruiser.backstack.BackstackEntry
 import de.gaw.kruiser.backstack.ui.ScreenContent
 import de.gaw.kruiser.backstack.ui.util.collectEntries
 import de.gaw.kruiser.backstack.util.rememberPreviousBackstackOf
-import de.gaw.kruiser.destination.Destination
 
 interface ScreenAnimationContext {
  val backstack: Backstack
@@ -25,7 +25,7 @@ private data class ScreenAnimationContextImpl(
  override val previousEntries: BackstackEntries,
 ) : ScreenAnimationContext
 
-typealias ScreenAnimationSpec = AnimatedContentTransitionScope<Destination?>.(ScreenAnimationContext) -> ContentTransform
+typealias ScreenAnimationSpec = AnimatedContentTransitionScope<BackstackEntry?>.(ScreenAnimationContext) -> ContentTransform
 
 @Composable
 fun ScreenAnimation(
@@ -53,10 +53,10 @@ fun ScreenAnimation(
  )
  },
  label = label,
- ) { destination ->
- when (destination) {
+ ) { entry ->
+ when (entry) {
  null -> Spacer(modifier = modifier.fillMaxSize())
- else -> ScreenContent(destination)
+ else -> ScreenContent(entry)
  }
  }
 }

kruiser/src/main/java/de/gaw/kruiser/backstack/ui/util/RememberSaveableBackstack.kt

@@ -4,6 +4,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.saveable.Saver
 import androidx.compose.runtime.saveable.rememberSaveable
 import de.gaw.kruiser.backstack.BackstackEntries
+import de.gaw.kruiser.backstack.BackstackEntry
 import de.gaw.kruiser.backstack.MutableBackstack
 import de.gaw.kruiser.destination.Destination
 
@@ -16,12 +17,13 @@ fun rememberSaveableBackstack(initial: BackstackEntries = emptyList()) = remembe
 }
 
 @Composable
-fun rememberSaveableBackstack(initial: Destination) = rememberSaveableBackstack(listOf(initial))
+fun rememberSaveableBackstack(initial: Destination) =
+ rememberSaveableBackstack(listOf(BackstackEntry(initial)))
 
-fun mutableBackstackSaver(): Saver<MutableBackstack, List<Destination>> =
+fun mutableBackstackSaver(): Saver<MutableBackstack, List<BackstackEntry>> =
  MutableBackstackSaver
 
-private val MutableBackstackSaver = Saver<MutableBackstack, List<Destination>>(
+private val MutableBackstackSaver = Saver<MutableBackstack, List<BackstackEntry>>(
  save = { it.entries.value.toList() },
  restore = { entries ->
  MutableBackstack(initial = entries)

kruiser/src/main/java/de/gaw/kruiser/destination/Destination.kt

@@ -1,11 +1,12 @@
 package de.gaw.kruiser.destination
 
 import androidx.compose.runtime.Composable
+import java.io.Serializable
 
 /**
  * May potentially live forever
  */
-interface Destination {
+interface Destination : Serializable {
  fun build(): Screen
 }
 

kruiser/src/main/java/de/gaw/kruiser/viewmodel/BackstackViewModelStoreOwner.kt

@@ -0,0 +1,77 @@
+package de.gaw.kruiser.viewmodel
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelStore
+import androidx.lifecycle.ViewModelStoreOwner
+import de.gaw.kruiser.backstack.Backstack
+import de.gaw.kruiser.backstack.BackstackEntry
+import de.gaw.kruiser.backstack.currentEntries
+import de.gaw.kruiser.destination.Destination
+
+/**
+ * Holds the [ViewModelStoreOwner]s for [Destination]s, allowing [ViewModel]s to be scoped to
+ * [BackstackEntry]s.
+ */
+private object BackstackViewModelStoreOwner {
+ private val viewModelStoreOwners: MutableMap<BackstackEntry, ViewModelStoreOwner> = mutableMapOf()
+
+ fun remove(entry: BackstackEntry) = viewModelStoreOwners.remove(entry)
+
+ operator fun get(entry: BackstackEntry): ViewModelStoreOwner {
+ return when (val owner = viewModelStoreOwners[entry]) {
+ null -> object : ViewModelStoreOwner {
+ override val viewModelStore: ViewModelStore = ViewModelStore()
+ }.also {
+ viewModelStoreOwners[entry] = it
+ }
+
+ else -> owner
+ }
+ }
+}
+
+/**
+ * Creates a [ViewModelStoreOwner] for the current [BackstackEntry]
+ *
+ * @param entry: The [BackstackEntry] to scope the [ViewModelStoreOwner] to.
+ * @param disposeWhen: Checks whether the [ViewModel]s should be disposed, can be called whenever the system requires it.
+ * This enables arbitrary scoping of [ViewModel]s, for Android Default behavior see the implementation of [Backstack.viewModelStoreOwner].
+ */
+@Composable
+fun backstackEntryViewModelStoreOwner(
+ entry: BackstackEntry,
+ disposeWhen: (BackstackEntry) -> Boolean,
+): ViewModelStoreOwner {
+ val backstackEntryViewModelStoreOwner = BackstackViewModelStoreOwner[entry]
+
+ val currentCanDispose by rememberUpdatedState(disposeWhen)
+ DisposableEffect(entry, backstackEntryViewModelStoreOwner) {
+ onDispose {
+ if (currentCanDispose(entry)) {
+ backstackEntryViewModelStoreOwner.viewModelStore.clear()
+ BackstackViewModelStoreOwner.remove(entry)
+ }
+ }
+ }
+
+ return backstackEntryViewModelStoreOwner
+}
+
+/**
+ * Creates a [ViewModelStoreOwner] for the current [BackstackEntry] using Android Default behavior
+ * of keeping the [ViewModel] around for as long as the [entry] is on the [Backstack].
+ *
+ * @param entry: The [BackstackEntry] to scope the [ViewModelStoreOwner] to.
+ */
+@Composable
+fun Backstack.viewModelStoreOwner(entry: BackstackEntry): ViewModelStoreOwner {
+ val currentBackstack by rememberUpdatedState(this)
+ return backstackEntryViewModelStoreOwner(
+ entry = entry,
+ disposeWhen = { !currentBackstack.currentEntries().contains(it) },
+ )
+}