Bind viewModel to composable lifecycle

gradle.properties

@@ -4,7 +4,7 @@ kotlin.mpp.enableGranularSourceSetsMetadata=true
 kotlin.native.enableDependencyPropagation=false
 
 #Android
-android.compileSdk=31
+android.compileSdk=32
 android.targetSdk=31
 android.minSdk=21
 
@@ -19,4 +19,6 @@ version.coreKtx=1.7.0
 version.appcompat=1.4.0
 version.material=1.4.0
 version.constraint=2.1.2
-version.lifecycleRuntimeKtx=2.4.0
+version.lifecycleRuntimeKtx=2.4.0
+version.viewModelKtx=2.4.0
+version.composeViewModel=2.6.0-alpha01

modo-render-android-compose/build.gradle.kts

@@ -20,6 +20,7 @@ android {
 
     kotlinOptions {
         jvmTarget = "1.8"
+        freeCompilerArgs += "-Xjvm-default=all"
     }
 
     buildFeatures {
@@ -36,6 +37,8 @@ dependencies {
     implementation("androidx.compose.ui:ui:${properties["version.compose"]}")
     implementation("androidx.compose.foundation:foundation:${properties["version.compose"]}")
     implementation("org.jetbrains.kotlin:kotlin-parcelize-runtime:${properties["version.kotlin"]}")
+    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:${properties["version.viewModelKtx"]}")
+    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:${properties["version.composeViewModel"]}")
 }
 
 val sourceJar by tasks.registering(Jar::class) {

modo-render-android-compose/src/main/java/com/github/terrakok/modo/android/compose/ComposeRender.kt

@@ -4,9 +4,11 @@ import android.app.Activity
 import androidx.compose.runtime.*
 import androidx.compose.runtime.saveable.SaveableStateHolder
 import androidx.compose.runtime.saveable.rememberSaveableStateHolder
+import androidx.lifecycle.ViewModelStoreOwner
 import com.github.terrakok.modo.NavigationRender
 import com.github.terrakok.modo.NavigationState
 import com.github.terrakok.modo.Screen
+import androidx.lifecycle.viewmodel.compose.LocalViewModelStoreOwner
 
 typealias RendererContent = @Composable ComposeRendererScope.() -> Unit
 
@@ -51,32 +53,51 @@ open class ComposeRenderImpl(
     private val lastStackEvent: MutableState<ScreenTransitionType> = mutableStateOf(ScreenTransitionType.Idle)
     private val removedScreens = mutableSetOf<Screen>()
 
+    private var viewModel: ModoViewModel? = null
+
     override fun invoke(state: NavigationState) {
         if (state.chain.isEmpty()) {
             exitAction()
         }
         lastStackEvent.value = getTransitionType(this.state.value.chain, state.chain)
         removedScreens.addAll(calculateRemovedScreens(this.state.value.chain, state.chain))
+
+        val oldState = this.state.value.chain
+        val newState = state.chain
+        if (oldState.size > newState.size) {
+            oldState.lastOrNull()?.let {
+                viewModel?.clear(it.id)
+            }
+        }
+
         this.state.value = state
     }
 
     @Composable
     override fun Content() {
+        val screen = state.value.chain.lastOrNull() ?: return
+        if (viewModel == null) {
+            val owner = checkNotNull(LocalViewModelStoreOwner.current) {
+                "No ViewModelStoreOwner was provided via LocalViewModelStoreOwner"
+            }
+            viewModel = ModoViewModel.getInstance(owner.viewModelStore)
+        }
+        val owner = ViewModelStoreOwner { viewModel!!.getViewModelStore(screen.id) }
+
         val stateHolder: SaveableStateHolder = rememberSaveableStateHolder()
         DisposableEffect(key1 = state.value) {
             onDispose {
                 clearStateHolder(stateHolder)
             }
         }
         CompositionLocalProvider(
-            LocalSaveableStateHolder provides stateHolder
+            LocalSaveableStateHolder provides stateHolder,
+            LocalViewModelStoreOwner provides owner
         ) {
-            state.value.chain.lastOrNull()?.let { screen ->
-                require(screen is ComposeScreen) {
-                    "ComposeRender works with ComposeScreen only! Received $screen"
-                }
-                ComposeRendererScope(screen, lastStackEvent.value).content()
+            require(screen is ComposeScreen) {
+                "ComposeRender works with ComposeScreen only! Received $screen"
             }
+            ComposeRendererScope(screen, lastStackEvent.value).content()
         }
     }
 

modo-render-android-compose/src/main/java/com/github/terrakok/modo/android/compose/ModoViewModel.kt

@@ -0,0 +1,53 @@
+package com.github.terrakok.modo.android.compose
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import androidx.lifecycle.ViewModelStore
+import androidx.lifecycle.get
+
+internal class ModoViewModel : ViewModel() {
+
+    private val viewModelStores = mutableMapOf<String, ViewModelStore>()
+
+    fun clear(key: String) {
+        val viewModelStore = viewModelStores.remove(key)
+        viewModelStore?.clear()
+    }
+
+    override fun onCleared() {
+        viewModelStores.values.forEach { it.clear() }
+        viewModelStores.clear()
+    }
+
+    fun getViewModelStore(key: String): ViewModelStore {
+        var viewModelStore = viewModelStores[key]
+        if (viewModelStore == null) {
+            viewModelStore = ViewModelStore()
+            viewModelStores[key] = viewModelStore
+        }
+        return viewModelStore
+    }
+
+    override fun toString(): String {
+        val sb = StringBuilder("ViewModelStores (")
+        val viewModelStoreIterator: Iterator<String> = viewModelStores.keys.iterator()
+        while (viewModelStoreIterator.hasNext()) {
+            sb.append(viewModelStoreIterator.next())
+            if (viewModelStoreIterator.hasNext()) {
+                sb.append(", ")
+            }
+        }
+        sb.append(')')
+        return sb.toString()
+    }
+
+    companion object {
+        private val factory: ViewModelProvider.Factory = object : ViewModelProvider.Factory {
+            @Suppress("UNCHECKED_CAST")
+            override fun <T : ViewModel> create(modelClass: Class<T>) = ModoViewModel() as T
+        }
+
+        fun getInstance(viewModelStore: ViewModelStore): ModoViewModel =
+            ViewModelProvider(viewModelStore, factory).get()
+    }
+}

sample-android-compose/build.gradle.kts

@@ -43,5 +43,6 @@ dependencies {
     implementation("androidx.compose.material:material:${properties["version.compose"]}")
     implementation("androidx.compose.ui:ui-tooling:${properties["version.compose"]}")
     implementation("androidx.lifecycle:lifecycle-runtime-ktx:${properties["version.lifecycleRuntimeKtx"]}")
+    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:${properties["version.composeViewModel"]}")
     implementation("androidx.activity:activity-compose:${properties["version.composeActivity"]}")
 }

sample-android-compose/src/main/java/com/github/terrakok/androidcomposeapp/saveable/DetailsScreen.kt

@@ -1,14 +1,17 @@
 package com.github.terrakok.androidcomposeapp.saveable
 
+import android.util.Log
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.material.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.lifecycle.ViewModel
 import com.github.terrakok.modo.android.compose.ComposeScreen
 import com.github.terrakok.modo.android.compose.uniqueScreenKey
 import kotlinx.parcelize.Parcelize
+import androidx.lifecycle.viewmodel.compose.viewModel
 
 @Parcelize
 class DetailsScreen(
@@ -24,10 +27,25 @@ class DetailsScreen(
 }
 
 @Composable
-fun ProfileDetailsScreen(id: String) {
+fun ProfileDetailsScreen(
+    id: String,
+    viewModel: DetailsViewModel = viewModel()
+) {
     Box {
         Column(Modifier.align(Alignment.Center)) {
             Text(text = "Profile details $id")
         }
     }
-}
+}
+
+class DetailsViewModel : ViewModel() {
+
+    init {
+        Log.d(this.javaClass.name, "init")
+    }
+
+    override fun onCleared() {
+        super.onCleared()
+        Log.d(this.javaClass.name, "onCleared")
+    }
+}