/*
* Copyright (C) 2019 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.camera.core;
import androidx.annotation.GuardedBy;
import androidx.annotation.NonNull;
import androidx.annotation.VisibleForTesting;
import androidx.camera.core.impl.UseCaseMediator;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.Lifecycle.State;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.OnLifecycleEvent;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* A repository of {@link UseCaseMediatorLifecycleController} instances.
*
* <p>Each {@link UseCaseMediatorLifecycleController} is associated with a {@link LifecycleOwner}
* that regulates the common lifecycle shared by all the use cases in the mediator.
*/
final class UseCaseMediatorRepository {
final Object mUseCasesLock = new Object();
@GuardedBy("mUseCasesLock")
final Map<LifecycleOwner, UseCaseMediatorLifecycleController>
mLifecycleToUseCaseMediatorControllerMap =
new HashMap<>();
@GuardedBy("mUseCasesLock")
final List<LifecycleOwner> mActiveLifecycleOwnerList = new ArrayList<>();
@GuardedBy("mUseCasesLock")
LifecycleOwner mCurrentActiveLifecycleOwner = null;
/**
* Gets an existing {@link UseCaseMediatorLifecycleController} associated with the given {@link
* LifecycleOwner}, or creates a new {@link UseCaseMediatorLifecycleController} if a mediator
* does not already exist.
*
* <p>The {@link UseCaseMediatorLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the mediator
*/
UseCaseMediatorLifecycleController getOrCreateUseCaseMediator(LifecycleOwner lifecycleOwner) {
return getOrCreateUseCaseMediator(lifecycleOwner, useCaseMediator -> {
});
}
/**
* Gets an existing {@link UseCaseMediatorLifecycleController} associated with the given {@link
* LifecycleOwner}, or creates a new {@link UseCaseMediatorLifecycleController} if a mediator
* does not already exist.
*
* <p>The {@link UseCaseMediatorLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the mediator
* @param mediatorSetup additional setup to do on the mediator if a new instance is created
*/
UseCaseMediatorLifecycleController getOrCreateUseCaseMediator(
LifecycleOwner lifecycleOwner, UseCaseMediatorSetup mediatorSetup) {
UseCaseMediatorLifecycleController useCaseMediatorLifecycleController;
synchronized (mUseCasesLock) {
useCaseMediatorLifecycleController = mLifecycleToUseCaseMediatorControllerMap.get(
lifecycleOwner);
if (useCaseMediatorLifecycleController == null) {
useCaseMediatorLifecycleController = createUseCaseMediator(lifecycleOwner);
mediatorSetup.setup(useCaseMediatorLifecycleController.getUseCaseMediator());
}
}
return useCaseMediatorLifecycleController;
}
/**
* Creates a new {@link UseCaseMediatorLifecycleController} associated with the given {@link
* LifecycleOwner} and adds the mediator to the repository.
*
* <p>The {@link UseCaseMediatorLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the mediator
* @return a new {@link UseCaseMediatorLifecycleController}
* @throws IllegalArgumentException if the {@link androidx.lifecycle.Lifecycle} of
* lifecycleOwner is already
* {@link androidx.lifecycle.Lifecycle.State.DESTROYED}.
*/
private UseCaseMediatorLifecycleController createUseCaseMediator(
LifecycleOwner lifecycleOwner) {
if (lifecycleOwner.getLifecycle().getCurrentState() == State.DESTROYED) {
throw new IllegalArgumentException(
"Trying to create use case mediator with destroyed lifecycle.");
}
// Need to add observer before creating UseCaseMediatorLifecycleController to make sure
// UseCaseMediators can be stopped before the latest active one is started.
lifecycleOwner.getLifecycle().addObserver(createLifecycleObserver());
UseCaseMediatorLifecycleController useCaseMediatorLifecycleController =
new UseCaseMediatorLifecycleController(lifecycleOwner.getLifecycle());
synchronized (mUseCasesLock) {
mLifecycleToUseCaseMediatorControllerMap.put(lifecycleOwner,
useCaseMediatorLifecycleController);
}
return useCaseMediatorLifecycleController;
}
/**
* Creates a {@link LifecycleObserver} to monitor state change of {@link LifecycleOwner}.
*
* @return a new {@link LifecycleObserver}
*/
private LifecycleObserver createLifecycleObserver() {
return new LifecycleObserver() {
/**
* Monitors which {@link LifecycleOwner} receives an ON_START event and then stop
* others {@link UseCaseMediator} to keep only one active at a time.
*/
@OnLifecycleEvent(Lifecycle.Event.ON_START)
public void onStart(LifecycleOwner lifecycleOwner) {
synchronized (mUseCasesLock) {
// Only keep the last {@link LifecycleOwner} active. Stop the others.
for (Map.Entry<LifecycleOwner, UseCaseMediatorLifecycleController> entry :
mLifecycleToUseCaseMediatorControllerMap.entrySet()) {
if (entry.getKey() != lifecycleOwner) {
UseCaseMediator useCaseMediator = entry.getValue().getUseCaseMediator();
if (useCaseMediator.isActive()) {
useCaseMediator.stop();
}
}
}
mCurrentActiveLifecycleOwner = lifecycleOwner;
mActiveLifecycleOwnerList.add(0, mCurrentActiveLifecycleOwner);
}
}
/**
* Monitors which {@link LifecycleOwner} receives an ON_STOP event.
*/
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
public void onStop(LifecycleOwner lifecycleOwner) {
synchronized (mUseCasesLock) {
// Removes stopped lifecycleOwner from active list.
mActiveLifecycleOwnerList.remove(lifecycleOwner);
if (mCurrentActiveLifecycleOwner == lifecycleOwner) {
// If stopped lifecycleOwner is original active one, check whether there
// is other active lifecycleOwner and start UseCaseMediator belong to it.
if (mActiveLifecycleOwnerList.size() > 0) {
mCurrentActiveLifecycleOwner = mActiveLifecycleOwnerList.get(0);
mLifecycleToUseCaseMediatorControllerMap.get(
mCurrentActiveLifecycleOwner).getUseCaseMediator().start();
} else {
mCurrentActiveLifecycleOwner = null;
}
}
}
}
/**
* Monitors which {@link LifecycleOwner} receives an ON_DESTROY event and then
* removes any {@link UseCaseMediatorLifecycleController} associated with it from this
* repository when that lifecycle is destroyed.
*/
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
public void onDestroy(LifecycleOwner lifecycleOwner) {
synchronized (mUseCasesLock) {
mLifecycleToUseCaseMediatorControllerMap.remove(lifecycleOwner);
}
lifecycleOwner.getLifecycle().removeObserver(this);
}
};
}
Collection<UseCaseMediatorLifecycleController> getUseCaseMediators() {
synchronized (mUseCasesLock) {
return Collections.unmodifiableCollection(
mLifecycleToUseCaseMediatorControllerMap.values());
}
}
@VisibleForTesting
Map<LifecycleOwner, UseCaseMediatorLifecycleController> getUseCasesMap() {
synchronized (mUseCasesLock) {
return mLifecycleToUseCaseMediatorControllerMap;
}
}
/**
* The interface for doing additional setup work on a newly created {@link UseCaseMediator}
* instance.
*/
public interface UseCaseMediatorSetup {
void setup(@NonNull UseCaseMediator useCaseMediator);
}
}