Universal-Image-Loader源码阅读（36）-DisplayBitmapTask

显示图片任务。

改种任务，直接显示图片，不需要先加载（已经加载过了）。

源码：

/** * Displays bitmap in {@link com.nostra13.universalimageloader.core.imageaware.ImageAware}. Must be called on UI thread. * * @author Sergey Tarasevich (nostra13[at]gmail[dot]com) * @see ImageLoadingListener * @see BitmapDisplayer * @since 1.3.1 */final class DisplayBitmapTask implements Runnable {private static final String LOG_DISPLAY_IMAGE_IN_IMAGEAWARE = "Display image in ImageAware (loaded from %1$s) [%2$s]";private static final String LOG_TASK_CANCELLED_IMAGEAWARE_REUSED = "ImageAware is reused for another image. Task is cancelled. [%s]";private static final String LOG_TASK_CANCELLED_IMAGEAWARE_COLLECTED = "ImageAware was collected by GC. Task is cancelled. [%s]";private final Bitmap bitmap;private final String imageUri;private final ImageAware imageAware;private final String memoryCacheKey;private final BitmapDisplayer displayer;private final ImageLoadingListener listener;private final ImageLoaderEngine engine;private final LoadedFrom loadedFrom;public DisplayBitmapTask(Bitmap bitmap, ImageLoadingInfo imageLoadingInfo, ImageLoaderEngine engine,LoadedFrom loadedFrom) {this.bitmap = bitmap;imageUri = imageLoadingInfo.uri;imageAware = imageLoadingInfo.imageAware;memoryCacheKey = imageLoadingInfo.memoryCacheKey;displayer = imageLoadingInfo.options.getDisplayer();listener = imageLoadingInfo.listener;this.engine = engine;this.loadedFrom = loadedFrom;}@Overridepublic void run() {if (imageAware.isCollected()) {//判断图片View是否已经被回收了，如果已经被回收，则取消任务L.d(LOG_TASK_CANCELLED_IMAGEAWARE_COLLECTED, memoryCacheKey);listener.onLoadingCancelled(imageUri, imageAware.getWrappedView());} else if (isViewWasReused()) {//图片View是否又用来展示其他图片了，如果是的话，则取消任务L.d(LOG_TASK_CANCELLED_IMAGEAWARE_REUSED, memoryCacheKey);listener.onLoadingCancelled(imageUri, imageAware.getWrappedView());} else {L.d(LOG_DISPLAY_IMAGE_IN_IMAGEAWARE, loadedFrom, memoryCacheKey);displayer.display(bitmap, imageAware, loadedFrom);engine.cancelDisplayTaskFor(imageAware);listener.onLoadingComplete(imageUri, imageAware.getWrappedView(), bitmap);}}/** Checks whether memory cache key (image URI) for current ImageAware is actual */private boolean isViewWasReused() {//判断View是否又用来展示其他图片了。此处要思考理解一下String currentCacheKey = engine.getLoadingUriForView(imageAware);return !memoryCacheKey.equals(currentCacheKey);}}