On a recent project I ran into a quirk/unexpected behavior when using MovieClipLoader in AS2 or Loader in AS3 to load an image. When using the classes, you have the ability to listen for a progress event, which you typically use to show an progress bar. If an image is cached, one would think the progress event would not fire since it should be fired on bytes loaded not bytes read, correct? Wrong. If an image is cached the progress event still fires, even to the tune of 9 times.
I would have not guessed this to be the case, and had even willingly drank the koolaid into believing all my load worries had been solved by these glorious classes. Instead I had to back peddle and use enterFrame checks for progress events and only use the onLoadInit/complete event from the class. All of this I found because a designer was getting upset because the progress bar kept showing up on loaded images. That’s right folks, the mantra here is “designers are your friends”.