Summary
This tutorial is about 9 pages long, and it is easy to get lost
in all the technical jargon, or worse, miss the grand unifying
theme of this tutorial. I'm going to try to explain the big
picture in a more human-understandable way.
Let's get back to the ladder, for
I have used the ladder example several times in this tutorial. The
XML file, like I mentioned earlier, is the ladder. Each pic node is the rung on the ladder.
If you have a lot of pictures specified in your XML file, your
ladder is increasingly taller because you now have more rungs/nodes.
Then, there is you - the explorer who is climbing the ladder to
see a bit further than what was visible before.
Each time you press the Next
Image button, you are simply climbing up the ladder - seeing
more of your surrounding that you had not seen earlier. Being
ever careful, you
check to make sure that you haven't reached the end of the
ladder, for it is tough to climb when you have nothing to climb
up on. Similarly, your photo gallery code checks to make sure
that it isn't the last image in the list. After all,
conventional wisdom is that you can't display what
does not exist.
You decide that you want to go
back down. For obvious reasons, you check to make sure that you are not already at
the bottom of the ladder. That is similar to how Flash checks to
make sure that it is not trying to load a previous image that
does not exist because it is currently on the first image
itself.
Of course, when you go up and
down on the ladder, you don't suddenly jolt to your new
elevation. You move smoothly from one rung to another rung on
your ladder. In Flash, when you switch images, you don't just
display your next image. You fade your new image into view in
the form of a simple transition that takes advantage of the
_alpha property.
Hopefully you don't preload data
while climbing a ladder, but you did tell Flash to preload your
new images before loading them into view. You accomplish that by checking to make sure
that the total file size of the image is the same size as the the image that
is currently being loaded. If the two file size checks are not
equal, you display a small progress bar that informs your
visitors about the progress. If the amount loaded
equals the total file size, that means the image is fully loaded
and ready for display.
Phew - this tutorial went a little longer than I
had expected! I have provided the source files for you to use in
MX 2004 and MX format:
Just a final word before we wrap up. If you have a question and/or want to be part of a friendly, collaborative community of over 220k other developers like yourself, post on the forums for a quick response!
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Photo Gallery
Using XML and Flash
