1 /*
2  * Copyright (C) 2024 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 package androidx.window.extensions.util;
17 
18 import androidx.annotation.GuardedBy;
19 import androidx.annotation.NonNull;
20 import androidx.annotation.Nullable;
21 import androidx.window.extensions.core.util.function.Consumer;
22 
23 /**
24  * A utility class that will not report a value if it is the same as the last reported value.
25  * @param <T> generic values to be reported.
26  */
27 public class DeduplicateConsumer<T> implements Consumer<T> {
28 
29     private final Object mLock = new Object();
30     @GuardedBy("mLock")
31     @Nullable
32     private T mLastReportedValue = null;
33     @NonNull
34     private final Consumer<T> mConsumer;
35 
DeduplicateConsumer(@onNull Consumer<T> consumer)36     public DeduplicateConsumer(@NonNull Consumer<T> consumer) {
37         mConsumer = consumer;
38     }
39 
40     /**
41      * Returns {@code true} if the given consumer matches this object or the wrapped
42      * {@link Consumer}, {@code false} otherwise
43      */
matchesConsumer(@onNull Consumer<T> consumer)44     public boolean matchesConsumer(@NonNull Consumer<T> consumer) {
45         return consumer == this || mConsumer.equals(consumer);
46     }
47 
48     /**
49      * Accepts a new value and relays it if it is different from
50      * the last reported value.
51      * @param value to report if different.
52      */
53     @Override
accept(@onNull T value)54     public void accept(@NonNull T value) {
55         synchronized (mLock) {
56             if (mLastReportedValue != null && mLastReportedValue.equals(value)) {
57                 return;
58             }
59             mLastReportedValue = value;
60         }
61         mConsumer.accept(value);
62     }
63 }
64