1 /*
2  * Copyright (C) 2021 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  * Produces data through {@link DataProducer#getData} and provides a mechanism for receiving
25  * a callback when the data managed by the produces has changed.
26  *
27  * @param <T> The type of data this producer returns through {@link DataProducer#getData}.
28  */
29 public interface DataProducer<T> {
30     /**
31      * Emits the first available data at that point in time.
32      * @param dataConsumer a {@link Consumer} that will receive one value.
33      */
getData(@onNull Consumer<T> dataConsumer)34     void getData(@NonNull Consumer<T> dataConsumer);
35 
36     /**
37      * Adds a callback to be notified when the data returned
38      * from {@link DataProducer#getData} has changed.
39      */
addDataChangedCallback(@onNull Consumer<T> callback)40     void addDataChangedCallback(@NonNull Consumer<T> callback);
41 
42     /** Removes a callback previously added with {@link #addDataChangedCallback(Consumer)}. */
removeDataChangedCallback(@onNull Consumer<T> callback)43     void removeDataChangedCallback(@NonNull Consumer<T> callback);
44 }
45