| /* |
| * Copyright (C) 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.android.camera.async; |
| |
| import com.android.camera.util.Callback; |
| import com.google.common.base.Function; |
| import com.google.common.base.Supplier; |
| import com.google.common.util.concurrent.MoreExecutors; |
| |
| import java.util.List; |
| import java.util.concurrent.Executor; |
| |
| import javax.annotation.CheckReturnValue; |
| import javax.annotation.Nonnull; |
| import javax.annotation.ParametersAreNonnullByDefault; |
| |
| /** |
| * Helper methods for {@link Observable}. |
| */ |
| @ParametersAreNonnullByDefault |
| public class Observables { |
| private static final SafeCloseable NOOP_CALLBACK_HANDLE = new SafeCloseable() { |
| @Override |
| public void close() { |
| // Do Nothing. |
| } |
| }; |
| |
| private Observables() { |
| } |
| |
| /** |
| * Transforms an observable with a function. |
| * |
| * @return The transformed observable. |
| */ |
| public static <F, T> Observable<T> transform(final Observable<F> input, |
| final Function<F, T> function) { |
| return new Observable<T>() { |
| @Nonnull |
| @Override |
| public T get() { |
| return function.apply(input.get()); |
| } |
| |
| @CheckReturnValue |
| @Nonnull |
| @Override |
| public SafeCloseable addCallback(Runnable callback, Executor executor) { |
| return input.addCallback(callback, executor); |
| } |
| }; |
| } |
| |
| /** |
| * @return An observable which recomputes its output every time an input changes. |
| */ |
| public static <T> Observable<T> transform(final List<? extends Observable<?>> inputs, |
| final Supplier<T> output) { |
| return ObservableCombiner.transform(inputs, output); |
| } |
| |
| /** |
| * Transforms a set of observables with a function. |
| * |
| * @return The transformed observable. |
| */ |
| public static <F, T> Observable<T> transform(final List<? extends Observable<F>> input, |
| Function<List<F>, T> function) { |
| return ObservableCombiner.transform(input, function); |
| } |
| |
| /** |
| * @return An observable which has the given constant value. |
| */ |
| @Nonnull |
| public static <T> Observable<T> of(final @Nonnull T constant) { |
| return new Observable<T>() { |
| @Nonnull |
| @Override |
| public T get() { |
| return constant; |
| } |
| |
| @CheckReturnValue |
| @Nonnull |
| @Override |
| public SafeCloseable addCallback(Runnable callback, Executor executor) { |
| return NOOP_CALLBACK_HANDLE; |
| } |
| }; |
| } |
| |
| @Nonnull |
| @CheckReturnValue |
| public static <T> SafeCloseable addThreadSafeCallback(final Observable<T> observable, |
| final Updatable<T> callback) { |
| return observable.addCallback(new Runnable() { |
| @Override |
| public void run() { |
| callback.update(observable.get()); |
| } |
| }, MoreExecutors.sameThreadExecutor()); |
| } |
| } |