| /* |
| * Copyright (C) 2020 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.internal.listeners; |
| |
| import android.annotation.Nullable; |
| |
| import java.util.Objects; |
| import java.util.concurrent.Executor; |
| import java.util.function.Consumer; |
| |
| /** |
| * A listener transport object which can run listener operations on an executor. |
| * |
| * @param <TListener> listener type |
| */ |
| public interface ListenerTransport<TListener> { |
| |
| /** |
| * Should return a valid listener until {@link #unregister()} is invoked, and must return |
| * null after that. Recommended (but not required) that this is implemented via a volatile |
| * variable. |
| */ |
| @Nullable TListener getListener(); |
| |
| /** |
| * Must be implemented so that {@link #getListener()} returns null after this is invoked. |
| */ |
| void unregister(); |
| |
| /** |
| * Executes the given operation for the listener. |
| */ |
| default void execute(Executor executor, Consumer<TListener> operation) { |
| Objects.requireNonNull(operation); |
| |
| if (getListener() == null) { |
| return; |
| } |
| |
| executor.execute(() -> { |
| TListener listener = getListener(); |
| if (listener == null) { |
| return; |
| } |
| |
| operation.accept(listener); |
| }); |
| } |
| } |