1 /*
2  * Copyright (C) 2022 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package androidx.window.util;
18 
19 import android.annotation.NonNull;
20 
21 import java.util.function.Consumer;
22 
23 /**
24  * A base class that works with {@link BaseDataProducer} to add/remove a consumer that should
25  * only be used once when {@link BaseDataProducer#notifyDataChanged} is called.
26  * @param <T> The type of data this producer returns through {@link DataProducer#getData}.
27  */
28 public class AcceptOnceConsumer<T> implements Consumer<T> {
29     private final Consumer<T> mCallback;
30     private final AcceptOnceProducerCallback<T> mProducer;
31 
AcceptOnceConsumer(@onNull AcceptOnceProducerCallback<T> producer, @NonNull Consumer<T> callback)32     public AcceptOnceConsumer(@NonNull AcceptOnceProducerCallback<T> producer,
33             @NonNull Consumer<T> callback) {
34         mProducer = producer;
35         mCallback = callback;
36     }
37 
38     @Override
accept(@onNull T t)39     public void accept(@NonNull T t) {
40         mCallback.accept(t);
41         mProducer.onConsumerReadyToBeRemoved(this);
42     }
43 
44     /**
45      * Interface to allow the {@link AcceptOnceConsumer} to notify the client that created it,
46      * when it is ready to be removed. This allows the client to remove the consumer object
47      * when it deems it is safe to do so.
48      * @param <T> The type of data this callback accepts through {@link #onConsumerReadyToBeRemoved}
49      */
50     public interface AcceptOnceProducerCallback<T> {
51 
52         /**
53          * Notifies that the given {@code callback} is ready to be removed
54          */
onConsumerReadyToBeRemoved(Consumer<T> callback)55         void onConsumerReadyToBeRemoved(Consumer<T> callback);
56     }
57 }
58