WorkManagerLiveDataTracker.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.work.impl;
import androidx.annotation.Nullable;
import androidx.annotation.VisibleForTesting;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MediatorLiveData;
import androidx.lifecycle.Observer;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Set;
/**
* Utility class that create LiveData instances which stay in memory as long as there is an
* active observer.
* see: b/74477406 for details.
*/
class WorkManagerLiveDataTracker {
@VisibleForTesting
final Set<LiveData> mLiveDataSet = Collections.newSetFromMap(
new IdentityHashMap<LiveData, Boolean>());
public <T> LiveData<T> track(LiveData<T> other) {
return new TrackedLiveData<>(this, other);
}
void onActive(LiveData liveData) {
mLiveDataSet.add(liveData);
}
void onInactive(LiveData liveData) {
mLiveDataSet.remove(liveData);
}
static class TrackedLiveData<T> extends MediatorLiveData<T> {
private final WorkManagerLiveDataTracker mContainer;
TrackedLiveData(WorkManagerLiveDataTracker container, LiveData<T> wrapped) {
mContainer = container;
addSource(wrapped, new Observer<T>() {
@Override
public void onChanged(@Nullable T t) {
setValue(t);
}
});
}
@Override
protected void onActive() {
super.onActive();
mContainer.onActive(this);
}
@Override
protected void onInactive() {
super.onInactive();
mContainer.onInactive(this);
}
}
}