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/*
* Copyright (C) 2021 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.window.util;
import android.annotation.Nullable;
import java.util.List;
import java.util.Optional;
/**
* Implementation of {@link DataProducer} that delegates calls to {@link #getData()} to the list of
* provided child producers.
* <p>
* The value returned is based on the precedence of the supplied children where the producer with
* index 0 has a higher precedence than producers that come later in the list. When a producer with
* a higher precedence has a non-empty value returned from {@link #getData()}, its value will be
* returned from an instance of this class, ignoring all other producers with lower precedence.
*
* @param <T> The type of data this producer returns through {@link #getData()}.
*/
public final class PriorityDataProducer<T> extends BaseDataProducer<T> {
private final List<DataProducer<T>> mChildProducers;
public PriorityDataProducer(List<DataProducer<T>> childProducers) {
mChildProducers = childProducers;
for (DataProducer<T> childProducer : mChildProducers) {
childProducer.addDataChangedCallback(this::notifyDataChanged);
}
}
@Nullable
@Override
public Optional<T> getData() {
for (DataProducer<T> childProducer : mChildProducers) {
final Optional<T> data = childProducer.getData();
if (data.isPresent()) {
return data;
}
}
return Optional.empty();
}
}
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