Batch preloading

Question

I would like to preload several thumbnails at once. What I
mean by that
is that I would load for example 10 jpgs that each will by
20k, but the
preloader would show progress for all of them at 200k. Of
course I would
like this to be dynamic, where flash will look and see how
large the
jpgs are to determining how much to preload. Is this
possible, or oven
good to do?
Thanks,
Brian

Answer 1

For AS2:
Its not - as I understand it - possible to do this accurately
without letting flash know the total bytesizes before hand. Flash
can't check the size before downloading. And even as it starts, the
information is not correct until the first onLoadProgress event for
each MovieClipLoader. There are two ways to overcome this if you
have a 'MultiLoader' style class which either queues or attempts
multiple simultaneous downloads.
1. To accurately reflect the progress, store the information
about the jpgs in an external xml file. So the xml would have the
image names, their urls and their total byte size as well. With
this data ahead of the loading process its then possible to create
the type of accurate feedback of progress that you want. The data
you get from a MovieClipLoader is incorrect in the early stages of
a load. This definitely applies to getBytesTotal - I can't remember
if getBytesLoaded is incorrect data as well before the first
onLoadProgress event. So if you do it this way (and the data about
the images in the xml is correct) you should just maintain an array
of BytesLoaded data which is updated at the correct index for each
loading clip from your onLoadProgress events. And you can dispatch
a groupProgress event which would give the sum of the elements in
the array as the groupBytesLoaded.
2. Another option is to check the validity of each clip's
data first before reporting it as part of the total. You only
report the group's progress in terms of a) valid bytesLoaded b)
valid bytesTotal c)number of 'valid' clips as a percent of total
number of clips. In this case a/b * c is an approximation of the
group progress. I works OK if the images are all going to be around
the same byte size, but it is only an 'approximation' attributing
an equal proportion of the total group progress to each image.
I very recently built a class that queues image loading using
the second approach above, inspired by some work David Stiller had
done on a MultiLoader class and the associated comments in his
blog, but using a different approach for validating individual clip
data and handling of individual MovieClipLoader listeners. You
might want to read it - David outlines some of the issues in more
detail with examples here:
http://www.quip.net/blog/2007/flash/actionscript-20/tracking-multiple-files-part1
http://www.quip.net/blog/2007/flash/actionscript-20/tracking-multiple-files-part2