UseCaseGroupRepository.java
/*
* 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.VisibleForTesting;
import androidx.camera.core.impl.UseCaseGroup;
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 UseCaseGroupLifecycleController} instances.
*
* <p>Each {@link UseCaseGroupLifecycleController} is associated with a {@link LifecycleOwner} that
* regulates the common lifecycle shared by all the use cases in the group.
*/
final class UseCaseGroupRepository {
final Object mUseCasesLock = new Object();
@GuardedBy("mUseCasesLock")
final Map<LifecycleOwner, UseCaseGroupLifecycleController>
mLifecycleToUseCaseGroupControllerMap =
new HashMap<>();
@GuardedBy("mUseCasesLock")
final List<LifecycleOwner> mActiveLifecycleOwnerList = new ArrayList<>();
@GuardedBy("mUseCasesLock")
LifecycleOwner mCurrentActiveLifecycleOwner = null;
/**
* Gets an existing {@link UseCaseGroupLifecycleController} associated with the given {@link
* LifecycleOwner}, or creates a new {@link UseCaseGroupLifecycleController} if a group does not
* already exist.
*
* <p>The {@link UseCaseGroupLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the group
*/
UseCaseGroupLifecycleController getOrCreateUseCaseGroup(LifecycleOwner lifecycleOwner) {
return getOrCreateUseCaseGroup(lifecycleOwner, new UseCaseGroupSetup() {
@Override
public void setup(UseCaseGroup useCaseGroup) {
}
});
}
/**
* Gets an existing {@link UseCaseGroupLifecycleController} associated with the given {@link
* LifecycleOwner}, or creates a new {@link UseCaseGroupLifecycleController} if a group does not
* already exist.
*
* <p>The {@link UseCaseGroupLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the group
* @param groupSetup additional setup to do on the group if a new instance is created
*/
UseCaseGroupLifecycleController getOrCreateUseCaseGroup(
LifecycleOwner lifecycleOwner, UseCaseGroupSetup groupSetup) {
UseCaseGroupLifecycleController useCaseGroupLifecycleController;
synchronized (mUseCasesLock) {
useCaseGroupLifecycleController = mLifecycleToUseCaseGroupControllerMap.get(
lifecycleOwner);
if (useCaseGroupLifecycleController == null) {
useCaseGroupLifecycleController = createUseCaseGroup(lifecycleOwner);
groupSetup.setup(useCaseGroupLifecycleController.getUseCaseGroup());
}
}
return useCaseGroupLifecycleController;
}
/**
* Creates a new {@link UseCaseGroupLifecycleController} associated with the given {@link
* LifecycleOwner} and adds the group to the repository.
*
* <p>The {@link UseCaseGroupLifecycleController} is set to be an observer of the {@link
* LifecycleOwner}.
*
* @param lifecycleOwner to associate with the group
* @return a new {@link UseCaseGroupLifecycleController}
* @throws IllegalArgumentException if the {@link androidx.lifecycle.Lifecycle} of
* lifecycleOwner is already
* {@link androidx.lifecycle.Lifecycle.State.DESTROYED}.
*/
private UseCaseGroupLifecycleController createUseCaseGroup(LifecycleOwner lifecycleOwner) {
if (lifecycleOwner.getLifecycle().getCurrentState() == State.DESTROYED) {
throw new IllegalArgumentException(
"Trying to create use case group with destroyed lifecycle.");
}
// Need to add observer before creating UseCaseGroupLifecycleController to make sure
// UseCaseGroups can be stopped before the latest active one is started.
lifecycleOwner.getLifecycle().addObserver(createLifecycleObserver());
UseCaseGroupLifecycleController useCaseGroupLifecycleController =
new UseCaseGroupLifecycleController(lifecycleOwner.getLifecycle());
synchronized (mUseCasesLock) {
mLifecycleToUseCaseGroupControllerMap.put(lifecycleOwner,
useCaseGroupLifecycleController);
}
return useCaseGroupLifecycleController;
}
/**
* 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 UseCaseGroup} 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, UseCaseGroupLifecycleController> entry :
mLifecycleToUseCaseGroupControllerMap.entrySet()) {
if (entry.getKey() != lifecycleOwner) {
UseCaseGroup useCaseGroup = entry.getValue().getUseCaseGroup();
if (useCaseGroup.isActive()) {
useCaseGroup.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 UseCaseGroup belong to it.
if (mActiveLifecycleOwnerList.size() > 0) {
mCurrentActiveLifecycleOwner = mActiveLifecycleOwnerList.get(0);
mLifecycleToUseCaseGroupControllerMap.get(
mCurrentActiveLifecycleOwner).getUseCaseGroup().start();
} else {
mCurrentActiveLifecycleOwner = null;
}
}
}
}
/**
* Monitors which {@link LifecycleOwner} receives an ON_DESTROY event and then
* removes any {@link UseCaseGroupLifecycleController} associated with it from this
* repository when that lifecycle is destroyed.
*/
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
public void onDestroy(LifecycleOwner lifecycleOwner) {
synchronized (mUseCasesLock) {
mLifecycleToUseCaseGroupControllerMap.remove(lifecycleOwner);
}
lifecycleOwner.getLifecycle().removeObserver(this);
}
};
}
Collection<UseCaseGroupLifecycleController> getUseCaseGroups() {
synchronized (mUseCasesLock) {
return Collections.unmodifiableCollection(
mLifecycleToUseCaseGroupControllerMap.values());
}
}
@VisibleForTesting
Map<LifecycleOwner, UseCaseGroupLifecycleController> getUseCasesMap() {
synchronized (mUseCasesLock) {
return mLifecycleToUseCaseGroupControllerMap;
}
}
/**
* The interface for doing additional setup work on a newly created {@link UseCaseGroup}
* instance.
*/
public interface UseCaseGroupSetup {
void setup(UseCaseGroup useCaseGroup);
}
}