Observable.java revision e919a48fb40b9d6c698a495acf40adbc0e320431
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; 20import com.google.common.base.Supplier; 21 22import java.util.concurrent.Executor; 23 24import javax.annotation.CheckReturnValue; 25import javax.annotation.Nonnull; 26import javax.annotation.ParametersAreNonnullByDefault; 27import javax.annotation.concurrent.ThreadSafe; 28 29/** 30 * An interface for thread-safe observable objects. 31 */ 32@ThreadSafe 33@ParametersAreNonnullByDefault 34public interface Observable<T> extends Supplier<T> { 35 /** 36 * Adds the given callback, returning a handle to be closed when the 37 * callback must be deregistered. 38 * 39 * @param callback The callback to add. 40 * @param executor The executor on which the callback will be invoked. 41 * @return A handle to be closed when the callback must be removed. 42 */ 43 @Nonnull 44 @CheckReturnValue 45 public SafeCloseable addCallback(Callback<T> callback, Executor executor); 46 47 /** 48 * @return The current/latest value. 49 */ 50 @Nonnull 51 @Override 52 public T get(); 53} 54