| /* |
| * 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(); |
| } |
| } |