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 17 package com.android.camera.async; 18 19 import java.util.concurrent.Executor; 20 import java.util.concurrent.ScheduledExecutorService; 21 import java.util.concurrent.ScheduledFuture; 22 import java.util.concurrent.TimeUnit; 23 24 /** 25 * An executor which executes with a delay, discarding pending executions such 26 * that at most one task is queued at any time. 27 */ 28 public class ResettingDelayedExecutor implements Executor, SafeCloseable { 29 private final ScheduledExecutorService mExecutor; 30 private final long mDelay; 31 private final TimeUnit mDelayUnit; 32 /** 33 * Lock for all mutable state: {@link #mLatestRunRequest} and 34 * {@link #mClosed}. 35 */ 36 private final Object mLock; 37 private ScheduledFuture<?> mLatestRunRequest; 38 private boolean mClosed; 39 40 public ResettingDelayedExecutor(ScheduledExecutorService executor, long delay, TimeUnit 41 delayUnit) { 42 mExecutor = executor; 43 mDelay = delay; 44 mDelayUnit = delayUnit; 45 mLock = new Object(); 46 mClosed = false; 47 } 48 49 /** 50 * Resets any pending executions. 51 */ 52 public void reset() { 53 synchronized (mLock) { 54 // Cancel any existing, queued task before scheduling another. 55 if (mLatestRunRequest != null) { 56 mLatestRunRequest.cancel(false /* mayInterruptIfRunning */); 57 } 58 } 59 } 60 61 @Override 62 public void execute(Runnable runnable) { 63 synchronized (mLock) { 64 if (mClosed) { 65 return; 66 } 67 reset(); 68 mLatestRunRequest = mExecutor.schedule(runnable, mDelay, mDelayUnit); 69 } 70 } 71 72 @Override 73 public void close() { 74 synchronized (mLock) { 75 if (mClosed) { 76 return; 77 } 78 mClosed = true; 79 mExecutor.shutdownNow(); 80 } 81 } 82 } 83
