Observable.java revision 17fc13a74ff71e3c721218624815c244dccc33f7 
1/*
2 * Copyright (C) 2014 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
17package com.android.camera.async;
18
19import com.android.camera.util.Callback;
20
21import java.util.concurrent.Executor;
22
23/**
24 * An interface for thread-safe observable objects.
25 */
26public interface Observable<T> extends Pollable<T> {
27    /**
28     * Adds the given callback, returning a handle to be closed when the
29     * callback must be deregistered.
30     *
31     * @param callback The callback to add.
32     * @param executor The executor on which the callback will be invoked.
33     * @return A {@link SafeCloseable} handle to be closed when the callback
34     *         must be removed.
35     */
36    public SafeCloseable addCallback(Callback callback, Executor executor);
37}
38