Every time a new version of Macromedia Flash is released, there
are a number of new features that don't get a lot of press, but
make a huge difference in the day-to-day work of developers. Macromedia
Flash MX is, in fact, chock-full of such features. In this first
Flash MAX article I'd like to share the coolest new developer-centric
features that you might not know about.
Happy returns
First of all, I use the attachMovie method of the movieclip object
a lot. It was definitely one of my favorite features of Macromedia
Flash 5. Often when I use attachMovie, it's within a loop. I'll
create a movieclip dynamically, then make a "shortcut"
to it so that I don't have to keep evaluating it by name. That
shortcut can help save a lot of CPU cycles since evaluating a
string is a relatively expensive operation. The code looks like
this:
this.attachMovie("someClip", "foo"+i,
i);
temp = this["foo"+i];
It was to my immense amusement and surprise when I was told that
despite what the documentation says, attachMovie now returns a
reference to the movieclip it just created. So now, with Macromedia
Flash MX, the code can look like this:
temp = this.attachMovie("someClip",
"foo"+i, i);
In fact, two other methods of the movieclip object, duplicateMovieClip
and createNewMovieClip, also
return references to the clips they create.
Data du jour
If you take a look at the methods available inside of the combo
and list box components included with Macromedia Flash MX, you'll
see that they have a curious method called setDataProvider. The
actual documentation for this method recommends that users just
pass an array to the method, which will be used to fill the component.
However, the documentation also mentions an ActionScript object
called DataProviderClass. The DataProviderClass is located in
the asset folder of the component in the Library at:
/Flash UI Components/Core Assets - Developer Only/FUIComponent
Class Tree/DataProvider
If you bravely wander that deep into the "developer only"
parts of the components you'll find that the DataProviderClass
isn't actually all that complicated. It's essentially a high level
version of an array. The methods to really care about are:
addItem
addItemAt
removeItemAt
removeAll
replaceItemAt
getLength
getItemAt
All of these methods are pretty easy to understand once you look
at the code. This high level way of shuffling around data isn't
the really interesting part though. If you create an instance
of DataProviderClass, and wire it up to a combo or list box you
will have a live data connection between the data provider and
the component. That is, anytime you update your instance of DataProviderClass,
the component will update automatically. Assuming that combo_cb
is your combo box, the code would look like this do to that "wiring":
dp = new DataProviderClass();
combo_cb.setDataProvider(dp);
Even cooler is the fact that multiple components can all be tied
to one data provider and all updated anytime the data provider
is modified. This becomes particularly interesting when you notice
that a number of the components inside of the "Flash UI Components
2" and "Charting Components" libraries (which are
available from the Macromedia Exchange for Flash) also support
data providers.
Economy of scale
One new object in Macromedia Flash MX that most folks haven't
used much is the Stage object. Sure, you can get the size of the
stage from this object, and that's very helpful, but there's so
much more there!
Imagine if you will, that you could create a Flash movie in which
the contents would automatically re-arrange according to how much
"room" is available on the stage. So, if the user resizes
their browser the flash movie inside will know of that fact and
rearrange the contents of the Flash movie accordingly. No need
to imagine, you can do that now!
All you need to do is to utilize two properties of the Stage
object, scaleMode and align as well as properly set the publish
settings of your movie. First of all, in the HTML tab of your
publish settings, set the dimension of your movie to use percent
rather than 'match movie' or 'pixels'. Also, make sure that your
movie's scale option is set to 'Default (Show All)'. These two
options will make your movie scale to the size of the browser
window.
Now, somewhere in your movie add the following two lines of code:
Stage.scaleMode = "noScale";
Stage.align = "tl";
The first line will prevent the actual content of your movie
from scaling when the browser is scaled. The second line will
make sure that the content of your SWF is always aligned at the
top left. The reference info on Stage.align gives all of the other
possible options for it.
Finally, for your movie to "hear" when the stage is
resized, your have to set up a listener for the Stage object.
The documentation on Stage.addListener shows how to do this, but
in a nutshell your code will look like this:
this.onResize = function()
{
//resize code here
}
Stage.addListener(this);
Now, anytime the stage is resized the onResize function will
be called. Inside of the function you can simply use Stage.width
and Stage.height to find out the "actual" size of stage.
Mincing words
Finally (for this article only though, as there are dozens of
other lesser-known features in Flash MX) I'd like to highlight
an event that belongs to the new LoadVars object. LoadVars is
used to--you guessed it--load data from a URL. The event in question,
onData, is automatically called when a URL is loaded, but before
the raw information is parsed into name/value pairs. In fact,
that raw information from the URL loaded is passed to onData.
This is useful because sometimes you don't want name/value pairs,
you just want the raw information from a URL. For example, say
a text file contains information that a marketing person has to
update, like some advertising text.
To get to the raw data, just overwrite a LoadVars object's onData
event, like this:
info = new LoadVars();
info.onData = function(raw){
trace(raw);
}
info.load("somefile.txt");
Now, the raw variable inside of your onData method contains the
raw information from somefile.txt.
Conclusion
Macromedia Flash MX is a very complex and powerful tool, and as
such there is a lot more to it than meets the eye or appears in
marketing messages. Make sure you take some time to dig into the
product and find the features that will make your development
easier. There's almost always another new feature to discover
and learn about.
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