AsyncDrawable.java

  /**
	 * Common view components such as ListView and GridView recycle child views
	 * as users scrolls. If each child view triggers an load task, there is no
	 * guarantee when it completes, the associated view has not already been
	 * recycled for use in another child view, either for the order in which
	 * asynchronous tasks are started is the order that they complete.
	 * 
	 * This custom Drawable that will be attached to the imageView while the
	 * work is in progress. Contains a reference to the actual loading image,
	 * a.k.a the uid of the image being loading.
	 * 
	 * so that it can be stopped if a new binding is required, and makes sure
	 * that only the last started worker process can bind its result,
	 * independently of the finish order.
	 */

	static class AsyncDrawable extends BitmapDrawable {
		private String key;

		public AsyncDrawable(Resources res, Bitmap bitmap, String key) {
			super(res, bitmap);
			this.key = key;
		}

		public String getLoadTaskKey() {
			return this.key;
		}
	}