/*
* 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 static androidx.lifecycle.AbstractSavedStateViewModelFactory.TAG_SAVED_STATE_HANDLE_CONTROLLER;
import static androidx.lifecycle.LegacySavedStateHandleController.attachHandleIfNeeded;
import static androidx.lifecycle.SavedStateHandleSupport.createSavedStateHandle;
import static androidx.lifecycle.ViewModelProvider.NewInstanceFactory.VIEW_MODEL_KEY;
import android.annotation.SuppressLint;
import android.app.Application;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.lifecycle.ViewModelProvider.AndroidViewModelFactory;
import androidx.lifecycle.viewmodel.CreationExtras;
import androidx.savedstate.SavedStateRegistry;
import androidx.savedstate.SavedStateRegistryOwner;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.Arrays;
/**
* {@link androidx.lifecycle.ViewModelProvider.Factory} that can create ViewModels accessing and
* contributing to a saved state via {@link SavedStateHandle} received in a constructor.
* If {@code defaultArgs} bundle was passed into the constructor, it will provide default
* values in {@code SavedStateHandle}.
* <p>
* If ViewModel is instance of {@link androidx.lifecycle.AndroidViewModel}, it looks for a
* constructor that receives an {@link Application} and {@link SavedStateHandle} (in this order),
* otherwise it looks for a constructor that receives {@link SavedStateHandle} only.
* {@link androidx.lifecycle.AndroidViewModel} is only supported if you pass a non-null
* {@link Application} instance.
*/
public final class SavedStateViewModelFactory extends ViewModelProvider.OnRequeryFactory
implements ViewModelProvider.Factory {
private Application mApplication;
private final ViewModelProvider.Factory mFactory;
private Bundle mDefaultArgs;
private Lifecycle mLifecycle;
private SavedStateRegistry mSavedStateRegistry;
/**
* Constructs this factory.
* <p>
* When a factory is constructed this way, a component for which {@link SavedStateHandle} is
* scoped must have called
* {@link SavedStateHandleSupport#enableSavedStateHandles(SavedStateRegistryOwner)}.
* See {@link SavedStateHandleSupport#createSavedStateHandle(CreationExtras)} docs for more
* details.
*/
public SavedStateViewModelFactory() {
mFactory = new AndroidViewModelFactory();
}
/**
* Creates {@link SavedStateViewModelFactory}.
* <p>
* {@link androidx.lifecycle.ViewModel} created with this factory can access to saved state
* scoped to the given {@code activity}.
*
* @param application an application. If null, {@link AndroidViewModel} instances will not be
* supported.
* @param owner {@link SavedStateRegistryOwner} that will provide restored state for
* created
* {@link androidx.lifecycle.ViewModel ViewModels}
*/
public SavedStateViewModelFactory(@Nullable Application application,
@NonNull SavedStateRegistryOwner owner) {
this(application, owner, null);
}
/**
* Creates {@link SavedStateViewModelFactory}.
* <p>
* {@link androidx.lifecycle.ViewModel} created with this factory can access to saved state
* scoped to the given {@code activity}.
*
* @param application an application. If null, {@link AndroidViewModel} instances will not be
* supported.
* @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} if there is no previously saved state or
* previously saved state
* misses a value by such key.
*/
@SuppressLint("LambdaLast")
public SavedStateViewModelFactory(@Nullable Application application,
@NonNull SavedStateRegistryOwner owner,
@Nullable Bundle defaultArgs) {
mSavedStateRegistry = owner.getSavedStateRegistry();
mLifecycle = owner.getLifecycle();
mDefaultArgs = defaultArgs;
mApplication = application;
mFactory = application != null
? AndroidViewModelFactory.getInstance(application)
: ViewModelProvider.NewInstanceFactory.getInstance();
}
@NonNull
@Override
public <T extends ViewModel> T create(@NonNull Class<T> modelClass,
@NonNull CreationExtras extras) {
String key = extras.get(VIEW_MODEL_KEY);
if (key == null) {
throw new IllegalStateException(
"VIEW_MODEL_KEY must always be provided by ViewModelProvider");
}
// legacy constructor was called
if (mLifecycle != null) {
return create(key, modelClass);
}
Application application = extras.get(AndroidViewModelFactory.APPLICATION_KEY);
Constructor<T> constructor;
boolean isAndroidViewModel = AndroidViewModel.class.isAssignableFrom(modelClass);
if (isAndroidViewModel && application != null) {
constructor = findMatchingConstructor(modelClass, ANDROID_VIEWMODEL_SIGNATURE);
} else {
constructor = findMatchingConstructor(modelClass, VIEWMODEL_SIGNATURE);
}
// doesn't need SavedStateHandle
if (constructor == null) {
return mFactory.create(modelClass, extras);
}
T viewmodel;
if (isAndroidViewModel && application != null) {
viewmodel = newInstance(modelClass, constructor, application,
createSavedStateHandle(extras));
} else {
viewmodel = newInstance(modelClass, constructor, createSavedStateHandle(extras));
}
return viewmodel;
}
/**
* Creates a new instance of the given `Class`.
*
* @param key a key associated with the requested ViewModel
* @param modelClass a `Class` whose instance is requested
* @return a newly created ViewModel
*/
@NonNull
public <T extends ViewModel> T create(@NonNull String key, @NonNull Class<T> modelClass) {
// empty constructor was called.
if (mLifecycle == null) {
throw new UnsupportedOperationException(
"SavedStateViewModelFactory constructed "
+ "with empty constructor supports only calls to "
+ "create(modelClass: Class<T>, extras: CreationExtras)."
);
}
boolean isAndroidViewModel = AndroidViewModel.class.isAssignableFrom(modelClass);
Constructor<T> constructor;
if (isAndroidViewModel && mApplication != null) {
constructor = findMatchingConstructor(modelClass, ANDROID_VIEWMODEL_SIGNATURE);
} else {
constructor = findMatchingConstructor(modelClass, VIEWMODEL_SIGNATURE);
}
// doesn't need SavedStateHandle
if (constructor == null) {
return mFactory.create(modelClass);
}
SavedStateHandleController controller = LegacySavedStateHandleController.create(
mSavedStateRegistry, mLifecycle, key, mDefaultArgs);
T viewmodel;
if (isAndroidViewModel && mApplication != null) {
viewmodel = newInstance(modelClass, constructor, mApplication, controller.getHandle());
} else {
viewmodel = newInstance(modelClass, constructor, controller.getHandle());
}
viewmodel.setTagIfAbsent(TAG_SAVED_STATE_HANDLE_CONTROLLER, controller);
return viewmodel;
}
private static <T extends ViewModel> T newInstance(@NonNull Class<T> modelClass,
Constructor<T> constructor, Object... params) {
try {
return constructor.newInstance(params);
} catch (IllegalAccessException e) {
throw new RuntimeException("Failed to access " + modelClass, e);
} catch (InstantiationException e) {
throw new RuntimeException("A " + modelClass + " cannot be instantiated.", e);
} catch (InvocationTargetException e) {
throw new RuntimeException("An exception happened in constructor of "
+ modelClass, e.getCause());
}
}
@NonNull
@Override
public <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);
}
private static final Class<?>[] ANDROID_VIEWMODEL_SIGNATURE = new Class[]{Application.class,
SavedStateHandle.class};
private static final Class<?>[] VIEWMODEL_SIGNATURE = new Class[]{SavedStateHandle.class};
// it is done instead of getConstructor(), because getConstructor() throws an exception
// if there is no such constructor, which is expensive
@SuppressWarnings("unchecked")
private static <T> Constructor<T> findMatchingConstructor(Class<T> modelClass,
Class<?>[] signature) {
for (Constructor<?> constructor : modelClass.getConstructors()) {
Class<?>[] parameterTypes = constructor.getParameterTypes();
if (Arrays.equals(signature, parameterTypes)) {
return (Constructor<T>) constructor;
}
}
return null;
}
/**
* @hide
*/
@Override
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public void onRequery(@NonNull ViewModel viewModel) {
// needed only for legacy path
if (mLifecycle != null) {
attachHandleIfNeeded(viewModel, mSavedStateRegistry, mLifecycle);
}
}
}