Universal-Image-Loader源码阅读（38）-ImageLoaderEngine

作为该开源控件的核心处理器存在。

既然图片处理，就免不了异步处理，这不，其内部就定义了三个Executor。

源码：

/** * {@link ImageLoader} engine which responsible for {@linkplain LoadAndDisplayImageTask display task} execution. * * @author Sergey Tarasevich (nostra13[at]gmail[dot]com) * @since 1.7.1 */class ImageLoaderEngine {final ImageLoaderConfiguration configuration;private Executor taskExecutor;//任务处理-针对图片处理，以及图片下载private Executor taskExecutorForCachedImages;//图片已经缓存在硬件中的任务处理private Executor taskDistributor;//任务分发private final Map<Integer, String> cacheKeysForImageAwares = Collections.synchronizedMap(new HashMap<Integer, String>());private final Map<String, ReentrantLock> uriLocks = new WeakHashMap<String, ReentrantLock>();private final AtomicBoolean paused = new AtomicBoolean(false);private final AtomicBoolean networkDenied = new AtomicBoolean(false);private final AtomicBoolean slowNetwork = new AtomicBoolean(false);private final Object pauseLock = new Object();ImageLoaderEngine(ImageLoaderConfiguration configuration) {this.configuration = configuration;taskExecutor = configuration.taskExecutor;taskExecutorForCachedImages = configuration.taskExecutorForCachedImages;taskDistributor = DefaultConfigurationFactory.createTaskDistributor();}/** Submits task to execution pool */void submit(final LoadAndDisplayImageTask task) {//处理LoadAndDisplayImageTasktaskDistributor.execute(new Runnable() {//任务分发处理@Overridepublic void run() {File image = configuration.diskCache.get(task.getLoadingUri());//从硬件缓存中获取图片文件boolean isImageCachedOnDisk = image != null && image.exists();//是否硬件中有缓存的图片initExecutorsIfNeed();if (isImageCachedOnDisk) {//针对是否已有缓存，使用不同的处理器进行任务处理taskExecutorForCachedImages.execute(task);} else {taskExecutor.execute(task);}}});}/** Submits task to execution pool */void submit(ProcessAndDisplayImageTask task) {//处理ProcessAndDisplayImageTaskinitExecutorsIfNeed();taskExecutorForCachedImages.execute(task);//直接使用已有图片缓存的处理器处理任务}private void initExecutorsIfNeed() {//处理器初始化。如果不是自定义处理器，并且处理器已经中断了，则重新创建处理器if (!configuration.customExecutor && ((ExecutorService) taskExecutor).isShutdown()) {taskExecutor = createTaskExecutor();}if (!configuration.customExecutorForCachedImages && ((ExecutorService) taskExecutorForCachedImages).isShutdown()) {taskExecutorForCachedImages = createTaskExecutor();}}private Executor createTaskExecutor() {return DefaultConfigurationFactory.createExecutor(configuration.threadPoolSize, configuration.threadPriority,configuration.tasksProcessingType);}/** * Returns URI of image which is loading at this moment into passed {@link com.nostra13.universalimageloader.core.imageaware.ImageAware} */String getLoadingUriForView(ImageAware imageAware) {return cacheKeysForImageAwares.get(imageAware.getId());}/** * Associates <b>memoryCacheKey</b> with <b>imageAware</b>. Then it helps to define image URI is loaded into View at * exact moment. */void prepareDisplayTaskFor(ImageAware imageAware, String memoryCacheKey) {cacheKeysForImageAwares.put(imageAware.getId(), memoryCacheKey);}/** * Cancels the task of loading and displaying image for incoming <b>imageAware</b>. * * @param imageAware {@link com.nostra13.universalimageloader.core.imageaware.ImageAware} for which display task *                   will be cancelled */void cancelDisplayTaskFor(ImageAware imageAware) {cacheKeysForImageAwares.remove(imageAware.getId());}/** * Denies or allows engine to download images from the network.<br /> <br /> If downloads are denied and if image * isn't cached then {@link ImageLoadingListener#onLoadingFailed(String, View, FailReason)} callback will be fired * with {@link FailReason.FailType#NETWORK_DENIED} * * @param denyNetworkDownloads pass <b>true</b> - to deny engine to download images from the network; <b>false</b> - *                             to allow engine to download images from network. */void denyNetworkDownloads(boolean denyNetworkDownloads) {networkDenied.set(denyNetworkDownloads);}/** * Sets option whether ImageLoader will use {@link FlushedInputStream} for network downloads to handle <a * href="http://code.google.com/p/android/issues/detail?id=6066">this known problem</a> or not. * * @param handleSlowNetwork pass <b>true</b> - to use {@link FlushedInputStream} for network downloads; <b>false</b> *                          - otherwise. */void handleSlowNetwork(boolean handleSlowNetwork) {slowNetwork.set(handleSlowNetwork);}/** * Pauses engine. All new "load&display" tasks won't be executed until ImageLoader is {@link #resume() resumed}.<br * /> Already running tasks are not paused. */void pause() {paused.set(true);}/** Resumes engine work. Paused "load&display" tasks will continue its work. */void resume() {paused.set(false);synchronized (pauseLock) {pauseLock.notifyAll();}}/** * Stops engine, cancels all running and scheduled display image tasks. Clears internal data. * <br /> * <b>NOTE:</b> This method doesn't shutdown * {@linkplain com.nostra13.universalimageloader.core.ImageLoaderConfiguration.Builder#taskExecutor(java.util.concurrent.Executor) * custom task executors} if you set them. */void stop() {if (!configuration.customExecutor) {((ExecutorService) taskExecutor).shutdownNow();}if (!configuration.customExecutorForCachedImages) {((ExecutorService) taskExecutorForCachedImages).shutdownNow();}cacheKeysForImageAwares.clear();uriLocks.clear();}void fireCallback(Runnable r) {taskDistributor.execute(r);}ReentrantLock getLockForUri(String uri) {ReentrantLock lock = uriLocks.get(uri);if (lock == null) {lock = new ReentrantLock();uriLocks.put(uri, lock);}return lock;}AtomicBoolean getPause() {return paused;}Object getPauseLock() {return pauseLock;}boolean isNetworkDenied() {return networkDenied.get();}boolean isSlowNetwork() {return slowNetwork.get();}}