AbstractSavedStateViewModelFactory.java
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.lifecycle;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.savedstate.SavedStateRegistry;
import androidx.savedstate.SavedStateRegistryOwner;
/**
* Skeleton of androidx.lifecycle.ViewModelProvider.KeyedFactory
* that creates {@link SavedStateHandle} for every requested {@link androidx.lifecycle.ViewModel}.
* The subclasses implement {@link #create(String, Class, SavedStateHandle)} to actually instantiate
* {@code androidx.lifecycle.ViewModel}s.
*/
public abstract class AbstractSavedStateViewModelFactory extends ViewModelProvider.KeyedFactory {
static final String TAG_SAVED_STATE_HANDLE_CONTROLLER = "androidx.lifecycle.savedstate.vm.tag";
private final SavedStateRegistry mSavedStateRegistry;
private final Lifecycle mLifecycle;
private final Bundle mDefaultArgs;
/**
* Constructs this factory.
*
* @param owner {@link SavedStateRegistryOwner} that will provide restored state for created
* {@link androidx.lifecycle.ViewModel ViewModels}
* @param defaultArgs values from this {@code Bundle} will be used as defaults by
* {@link SavedStateHandle} passed in {@link ViewModel ViewModels}
* if there is no previously saved state
* or previously saved state misses a value by such key
*/
public AbstractSavedStateViewModelFactory(@NonNull SavedStateRegistryOwner owner,
@Nullable Bundle defaultArgs) {
mSavedStateRegistry = owner.getSavedStateRegistry();
mLifecycle = owner.getLifecycle();
mDefaultArgs = defaultArgs;
}
// TODO: make KeyedFactory#create(String, Class) package private
/**
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
@NonNull
@Override
public final <T extends ViewModel> T create(@NonNull String key, @NonNull Class<T> modelClass) {
Bundle restoredState = mSavedStateRegistry.consumeRestoredStateForKey(key);
SavedStateHandle handle = SavedStateHandle.createHandle(restoredState, mDefaultArgs);
SavedStateHandleController controller = new SavedStateHandleController(key, handle);
controller.attachToLifecycle(mSavedStateRegistry, mLifecycle);
T viewmodel = create(key, modelClass, handle);
viewmodel.setTagIfAbsent(TAG_SAVED_STATE_HANDLE_CONTROLLER, controller);
mSavedStateRegistry.runOnNextRecreation(OnRecreation.class);
return viewmodel;
}
@NonNull
@Override
public final <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
// ViewModelProvider calls correct create that support same modelClass with different keys
// If a developer manually calls this method, there is no "key" in picture, so factory
// simply uses classname internally as as key.
String canonicalName = modelClass.getCanonicalName();
if (canonicalName == null) {
throw new IllegalArgumentException("Local and anonymous classes can not be ViewModels");
}
return create(canonicalName, modelClass);
}
/**
* Creates a new instance of the given {@code Class}.
* <p>
*
* @param key a key associated with the requested ViewModel
* @param modelClass a {@code Class} whose instance is requested
* @param handle a handle to saved state associated with the requested ViewModel
* @param <T> The type parameter for the ViewModel.
* @return a newly created ViewModels
*/
@NonNull
protected abstract <T extends ViewModel> T create(@NonNull String key,
@NonNull Class<T> modelClass, @NonNull SavedStateHandle handle);
static final class OnRecreation implements SavedStateRegistry.AutoRecreated {
@Override
public void onRecreated(@NonNull SavedStateRegistryOwner owner) {
if (!(owner instanceof ViewModelStoreOwner)) {
throw new IllegalStateException(
"Internal error: OnRecreation should be registered only on components"
+ "that implement ViewModelStoreOwner");
}
ViewModelStore viewModelStore = ((ViewModelStoreOwner) owner).getViewModelStore();
SavedStateRegistry savedStateRegistry = owner.getSavedStateRegistry();
for (String key : viewModelStore.keys()) {
ViewModel viewModel = viewModelStore.get(key);
SavedStateHandleController controller = viewModel.getTag(
TAG_SAVED_STATE_HANDLE_CONTROLLER);
if (controller != null && !controller.isAttached()) {
controller.attachToLifecycle(owner.getSavedStateRegistry(),
owner.getLifecycle());
}
}
if (!viewModelStore.keys().isEmpty()) {
savedStateRegistry.runOnNextRecreation(OnRecreation.class);
}
}
}
static final class SavedStateHandleController implements LifecycleEventObserver {
private final String mKey;
boolean mIsAttached = false;
private final SavedStateHandle mHandle;
SavedStateHandleController(String key, SavedStateHandle handle) {
mKey = key;
mHandle = handle;
}
boolean isAttached() {
return mIsAttached;
}
void attachToLifecycle(SavedStateRegistry registry, Lifecycle lifecycle) {
if (mIsAttached) {
throw new IllegalStateException("Already attached to lifecycleOwner");
}
mIsAttached = true;
lifecycle.addObserver(this);
registry.registerSavedStateProvider(mKey, mHandle.savedStateProvider());
}
@Override
public void onStateChanged(@NonNull LifecycleOwner source, @NonNull Lifecycle.Event event) {
if (event == Lifecycle.Event.ON_DESTROY) {
mIsAttached = false;
source.getLifecycle().removeObserver(this);
}
}
}
}