Remove dependency on ViewModels in enableSavedStateHandles()
Rather than requiring the creation of a ViewModel as part of
the call to enableSavedStateHandle(), defer that creation
until createSavedStateHandle() is actually called. This
ensures that enableSavedStateHandles() is safe to call before
the owner is attached to a Context, etc.
Relnote: "You can now retrieve a previously registered
`SavedStateProvider` from a `SavedStateRegistry` via
`getSavedStateProvider()`."
Test: updated tests
BUG: 215406268
Change-Id: I7ea470c1af0385b8bc9d8ca653c84cc8d224e6cf
diff --git a/lifecycle/lifecycle-viewmodel-savedstate/build.gradle b/lifecycle/lifecycle-viewmodel-savedstate/build.gradle
index 5d0a4f8..19e6693 100644
--- a/lifecycle/lifecycle-viewmodel-savedstate/build.gradle
+++ b/lifecycle/lifecycle-viewmodel-savedstate/build.gradle
@@ -34,7 +34,7 @@
dependencies {
api("androidx.annotation:annotation:1.0.0")
api("androidx.core:core-ktx:1.2.0")
- api("androidx.savedstate:savedstate:1.0.0")
+ api(projectOrArtifact(":savedstate:savedstate"))
api(projectOrArtifact(":lifecycle:lifecycle-livedata-core"))
api(projectOrArtifact(":lifecycle:lifecycle-viewmodel"))
api(libs.kotlinStdlib)
diff --git a/lifecycle/lifecycle-viewmodel-savedstate/src/androidTest/java/androidx/lifecycle/viewmodel/savedstate/SavedStateHandleSupportTest.kt b/lifecycle/lifecycle-viewmodel-savedstate/src/androidTest/java/androidx/lifecycle/viewmodel/savedstate/SavedStateHandleSupportTest.kt
index 04426af..12eff00 100644
--- a/lifecycle/lifecycle-viewmodel-savedstate/src/androidTest/java/androidx/lifecycle/viewmodel/savedstate/SavedStateHandleSupportTest.kt
+++ b/lifecycle/lifecycle-viewmodel-savedstate/src/androidTest/java/androidx/lifecycle/viewmodel/savedstate/SavedStateHandleSupportTest.kt
@@ -55,6 +55,7 @@
component.resume()
handle.set("a", "1")
val interim = component.recreate(keepingViewModels = true)
+ interim.enableSavedStateHandles()
handle.set("b", "2")
interim.resume()
diff --git a/lifecycle/lifecycle-viewmodel-savedstate/src/main/java/androidx/lifecycle/SavedStateHandleSupport.kt b/lifecycle/lifecycle-viewmodel-savedstate/src/main/java/androidx/lifecycle/SavedStateHandleSupport.kt
index 9e69f6f..47151f7 100644
--- a/lifecycle/lifecycle-viewmodel-savedstate/src/main/java/androidx/lifecycle/SavedStateHandleSupport.kt
+++ b/lifecycle/lifecycle-viewmodel-savedstate/src/main/java/androidx/lifecycle/SavedStateHandleSupport.kt
@@ -22,10 +22,13 @@
import androidx.annotation.MainThread
import androidx.lifecycle.ViewModelProvider.NewInstanceFactory.Companion.VIEW_MODEL_KEY
import androidx.lifecycle.viewmodel.CreationExtras
+import androidx.lifecycle.viewmodel.initializer
+import androidx.lifecycle.viewmodel.viewModelFactory
import androidx.savedstate.SavedStateRegistry
import androidx.savedstate.SavedStateRegistryOwner
private const val VIEWMODEL_KEY = "androidx.lifecycle.internal.SavedStateHandlesVM"
+private const val SAVED_STATE_KEY = "androidx.lifecycle.internal.SavedStateHandlesProvider"
/**
* Enables the support of [SavedStateHandle] in a component.
@@ -44,15 +47,13 @@
currentState == Lifecycle.State.INITIALIZED || currentState == Lifecycle.State.CREATED
)
- // make sure that SavedStateHandlesVM is created.
- ViewModelProvider(this, object : ViewModelProvider.Factory {
- override fun <T : ViewModel> create(modelClass: Class<T>): T {
- @Suppress("UNCHECKED_CAST")
- return SavedStateHandlesVM() as T
- }
- })[VIEWMODEL_KEY, SavedStateHandlesVM::class.java]
-
- savedStateRegistry.runOnNextRecreation(SavedStateHandleAttacher::class.java)
+ // Add the SavedStateProvider used to save SavedStateHandles
+ // if we haven't already registered the provider
+ if (savedStateRegistry.getSavedStateProvider(SAVED_STATE_KEY) == null) {
+ val provider = SavedStateHandlesProvider(savedStateRegistry, this)
+ savedStateRegistry.registerSavedStateProvider(SAVED_STATE_KEY, provider)
+ savedStateRegistry.runOnNextRecreation(SavedStateHandleAttacher::class.java)
+ }
}
private fun createSavedStateHandle(
@@ -61,22 +62,20 @@
key: String,
defaultArgs: Bundle?
): SavedStateHandle {
- val vm = viewModelStoreOwner.savedStateHandlesVM
- val savedStateRegistry = savedStateRegistryOwner.savedStateRegistry
- val handle = SavedStateHandle.createHandle(
- savedStateRegistry.consumeRestoredStateForKey(key), defaultArgs
- )
- val controller = SavedStateHandleController(key, handle)
- controller.attachToLifecycle(savedStateRegistry, savedStateRegistryOwner.lifecycle)
- vm.controllers.add(controller)
-
- return handle
+ val provider = savedStateRegistryOwner.savedStateHandlesProvider
+ val viewModel = viewModelStoreOwner.savedStateHandlesVM
+ // If we already have a reference to a previously created SavedStateHandle
+ // for a given key stored in our ViewModel, use that. Otherwise, create
+ // a new SavedStateHandle, providing it any restored state we might have saved
+ return viewModel.handles[key] ?: SavedStateHandle.createHandle(
+ provider.consumeRestoredStateForKey(key), defaultArgs
+ ).also { viewModel.handles[key] = it }
}
/**
* Creates `SavedStateHandle` that can be used in your ViewModels
*
- * This function requires `this.installSavedStateHandleSupport()` call during the component
+ * This function requires [enableSavedStateHandles] call during the component
* initialization. Latest versions of androidx components like `ComponentActivity`, `Fragment`,
* `NavBackStackEntry` makes this call automatically.
*
@@ -106,39 +105,94 @@
)
}
-internal object ThrowingFactory : ViewModelProvider.Factory {
- override fun <T : ViewModel> create(modelClass: Class<T>): T {
- throw IllegalStateException(
- "enableSavedStateHandles() wasn't called " +
- "prior to createSavedStateHandle() call"
- )
- }
-}
-
internal val ViewModelStoreOwner.savedStateHandlesVM: SavedStateHandlesVM
- get() =
- ViewModelProvider(this, ThrowingFactory)[VIEWMODEL_KEY, SavedStateHandlesVM::class.java]
+ get() = ViewModelProvider(this, viewModelFactory {
+ initializer { SavedStateHandlesVM() }
+ })[VIEWMODEL_KEY, SavedStateHandlesVM::class.java]
+
+internal val SavedStateRegistryOwner.savedStateHandlesProvider: SavedStateHandlesProvider
+ get() = savedStateRegistry.getSavedStateProvider(SAVED_STATE_KEY) as? SavedStateHandlesProvider
+ ?: throw IllegalStateException("enableSavedStateHandles() wasn't called " +
+ "prior to createSavedStateHandle() call")
internal class SavedStateHandlesVM : ViewModel() {
- val controllers = mutableListOf<SavedStateHandleController>()
+ val handles = mutableMapOf<String, SavedStateHandle>()
+}
+
+/**
+ * This single SavedStateProvider is responsible for saving the state of every
+ * SavedStateHandle associated with the SavedState/ViewModel pair.
+ */
+internal class SavedStateHandlesProvider(
+ private val savedStateRegistry: SavedStateRegistry,
+ viewModelStoreOwner: ViewModelStoreOwner
+) : SavedStateRegistry.SavedStateProvider {
+ private var restored = false
+ private var restoredState: Bundle? = null
+
+ private val viewModel by lazy {
+ viewModelStoreOwner.savedStateHandlesVM
+ }
+
+ override fun saveState(): Bundle {
+ return Bundle().apply {
+ // Ensure that even if ViewModels aren't recreated after process death and recreation
+ // that we keep their state until they are recreated
+ if (restoredState != null) {
+ putAll(restoredState)
+ }
+ // But if we do have ViewModels, prefer their state over what we may
+ // have restored
+ viewModel.handles.forEach { (key, handle) ->
+ val savedState = handle.savedStateProvider().saveState()
+ if (savedState != Bundle.EMPTY) {
+ putBundle(key, savedState)
+ }
+ }
+ }.also {
+ // After we've saved the state, allow restoring a second time
+ restored = false
+ }
+ }
+
+ /**
+ * Restore the state from the SavedStateRegistry if it hasn't already been restored.
+ */
+ fun performRestore() {
+ if (!restored) {
+ restoredState = savedStateRegistry.consumeRestoredStateForKey(SAVED_STATE_KEY)
+ restored = true
+ // Grab a reference to the ViewModel for later usage when we saveState()
+ // This ensures that even if saveState() is called after the Lifecycle is
+ // DESTROYED, we can still save the state
+ viewModel
+ }
+ }
+
+ /**
+ * Restore the state associated with a particular SavedStateHandle, identified by its [key]
+ */
+ fun consumeRestoredStateForKey(key: String): Bundle? {
+ performRestore()
+ return restoredState?.getBundle(key).also {
+ restoredState?.remove(key)
+ if (restoredState?.isEmpty == true) {
+ restoredState = null
+ }
+ }
+ }
}
// it reconnects existent SavedStateHandles to SavedStateRegistryOwner when it is recreated
internal class SavedStateHandleAttacher : SavedStateRegistry.AutoRecreated {
override fun onRecreated(owner: SavedStateRegistryOwner) {
- if (owner !is ViewModelStoreOwner) {
- throw java.lang.IllegalStateException(
- "Internal error: SavedStateHandleAttacher should be registered only on components" +
- "that implement ViewModelStoreOwner"
- )
- }
- val viewModelStore = (owner as ViewModelStoreOwner).viewModelStore
- // if savedStateHandlesVM wasn't created previously, we shouldn't trigger a creation of it
- if (!viewModelStore.keys().contains(VIEWMODEL_KEY)) return
- owner.savedStateHandlesVM.controllers.forEach {
- it.attachToLifecycle(owner.savedStateRegistry, owner.lifecycle)
- }
- owner.savedStateRegistry.runOnNextRecreation(SavedStateHandleAttacher::class.java)
+ // if SavedStateHandlesProvider wasn't added previously, there's nothing for us to do
+ val provider = owner.savedStateRegistry
+ .getSavedStateProvider(SAVED_STATE_KEY) as? SavedStateHandlesProvider ?: return
+ // onRecreated() is called after the Lifecycle reaches CREATED, so we
+ // eagerly restore the state as part of this call to ensure it consumed
+ // even if no ViewModels are actually created during this cycle of the Lifecycle
+ provider.performRestore()
}
}
diff --git a/savedstate/savedstate/api/current.txt b/savedstate/savedstate/api/current.txt
index 71beea9..2d04ca6 100644
--- a/savedstate/savedstate/api/current.txt
+++ b/savedstate/savedstate/api/current.txt
@@ -3,6 +3,7 @@
public final class SavedStateRegistry {
method @MainThread public android.os.Bundle? consumeRestoredStateForKey(String);
+ method public androidx.savedstate.SavedStateRegistry.SavedStateProvider? getSavedStateProvider(String);
method @MainThread public boolean isRestored();
method @MainThread public void registerSavedStateProvider(String, androidx.savedstate.SavedStateRegistry.SavedStateProvider);
method @MainThread public void runOnNextRecreation(Class<? extends androidx.savedstate.SavedStateRegistry.AutoRecreated>);
diff --git a/savedstate/savedstate/api/public_plus_experimental_current.txt b/savedstate/savedstate/api/public_plus_experimental_current.txt
index 71beea9..2d04ca6 100644
--- a/savedstate/savedstate/api/public_plus_experimental_current.txt
+++ b/savedstate/savedstate/api/public_plus_experimental_current.txt
@@ -3,6 +3,7 @@
public final class SavedStateRegistry {
method @MainThread public android.os.Bundle? consumeRestoredStateForKey(String);
+ method public androidx.savedstate.SavedStateRegistry.SavedStateProvider? getSavedStateProvider(String);
method @MainThread public boolean isRestored();
method @MainThread public void registerSavedStateProvider(String, androidx.savedstate.SavedStateRegistry.SavedStateProvider);
method @MainThread public void runOnNextRecreation(Class<? extends androidx.savedstate.SavedStateRegistry.AutoRecreated>);
diff --git a/savedstate/savedstate/api/restricted_current.txt b/savedstate/savedstate/api/restricted_current.txt
index 71beea9..2d04ca6 100644
--- a/savedstate/savedstate/api/restricted_current.txt
+++ b/savedstate/savedstate/api/restricted_current.txt
@@ -3,6 +3,7 @@
public final class SavedStateRegistry {
method @MainThread public android.os.Bundle? consumeRestoredStateForKey(String);
+ method public androidx.savedstate.SavedStateRegistry.SavedStateProvider? getSavedStateProvider(String);
method @MainThread public boolean isRestored();
method @MainThread public void registerSavedStateProvider(String, androidx.savedstate.SavedStateRegistry.SavedStateProvider);
method @MainThread public void runOnNextRecreation(Class<? extends androidx.savedstate.SavedStateRegistry.AutoRecreated>);
diff --git a/savedstate/savedstate/src/main/java/androidx/savedstate/SavedStateRegistry.java b/savedstate/savedstate/src/main/java/androidx/savedstate/SavedStateRegistry.java
index adeae54..3bca4f1 100644
--- a/savedstate/savedstate/src/main/java/androidx/savedstate/SavedStateRegistry.java
+++ b/savedstate/savedstate/src/main/java/androidx/savedstate/SavedStateRegistry.java
@@ -114,6 +114,28 @@
}
/**
+ * Get a previously registered {@link SavedStateProvider}.
+ *
+ * @param key The key used to register the {@link SavedStateProvider} when it was registered
+ * with {@link #registerSavedStateProvider(String, SavedStateProvider)}.
+ * @return The {@link SavedStateProvider} previously registered with
+ * {@link #registerSavedStateProvider(String, SavedStateProvider)} or null if no provider
+ * has been registered with the given key.
+ * @see #registerSavedStateProvider(String, SavedStateProvider)
+ */
+ @Nullable
+ public SavedStateProvider getSavedStateProvider(@NonNull String key) {
+ SavedStateProvider provider = null;
+ for (Map.Entry<String, SavedStateProvider> entry : mComponents) {
+ if (entry.getKey().equals(key)) {
+ provider = entry.getValue();
+ break;
+ }
+ }
+ return provider;
+ }
+
+ /**
* Unregisters a component previously registered by the given {@code key}
*
* @param key a key with which a component was previously registered.
