http://ech.net/flexsamples/so.swf

(This Flex samples directory is starting to cry out for an index page.)

The local SharedObject feature of the Flash player is becoming more widely used. Pandora is one example of a site that uses it to persist application state. It accomplishes what cookies were originally intended to do, but does not involve the web server, and thus avoids many of the security concerns of cookies. But there are valid criticisms of this feature. The browsers do not ask the user for permission to write this potentially personal data to the disk, nor do they offer the user a straightforward way to purge this data from the system. Dig around in your personal documents area for a directory called #SharedObjects, then look inside to see what sites have written information to your disk. For more information, see the Wikipedia page on the subject.

Although insidious, this feature sure is handy for the Flex developer.

Effects may be reversed. By calling Effect.reverse() (or EffectInstance.reverse()), an Effect can be made to reverse direction on the spot and play all the way back to the beginning. You can reverse an Effect playing in reverse to make it go forward again. You can even start an Effect from the end and play it in reverse. This is exactly what I was looking for. Unfortunately, there is no way to specify in MXML that you wish the rollOutEffect of a UIComponent to be the reverse of its rollOverEffect. And there were some knots to untangle in getting this approach to work nicely. The results, for general consumption, are at the URL below. Source code is included.

http://ech.net/flexsamples/rollo.swf

http://ech.net/360flex2008/

Matt Chotin, Product Manager at Adobe delivers the keynote. “Adobe AIR is out the door!” “Flex 3 is out the door!” Despite abundant forewarning of this moment, the official launch announcement is exciting.

Matt and his Adobe colleagues keep the interest level high, presenting a succession of new and upcoming features. Test framework integration with support for Borland, HP and IBM test frameworks! Open source Blaze/DS! Thermo! Gumbo (Flex 4)! Vellum! Hydra! I cheer loudly at the announcement of Astro, an upcoming 3D perspective effects package (a poor man’s papervision); I am among only about 10 people doing so. I cheer again loudly at the announcement of the type-safe Vector collection type; I am among only about 5 people this time. Where have all the nerds gone?

Hey, the Allurent Desktop Connection is getting another demo! This was shown at last year’s Max, but here it is again. I’m sure that Allurent marketing will be happy to hear about this. The guy to my right, in response to the “Search by Color” feature: “Oh, wow!” Matt apologizes to Joe B. in advance of possible screw-ups as he starts the demo. I wonder how this is possible, because I know that Joe is probably going through Logan Airport security at this moment. I ask Matt about this afterward, and he claims to have sighted Joe in the crowd. Later I spot a Joe B. doppelganger among the conference attendees. Who is this man?

Matt finishes with a very, very silly slide/audio/video show about working at Adobe. It is worth the entire price of the conference to see. Footnote: as a presenter I am attending the conference for free, so this is rather weak praise. But it is a funny show.

The conference sessions are divided into three concurrent tracks. I set off on the Custom Components track, planning to stick with it, and enjoy some great talks about custom component building. In a discussion with Joe B. of my presentation a few days earlier, he mentioned that he had seen in previous conferences a lack of discussion of the practical points of custom component buiding, in particular the Flex component lifecycle functions. As if in rebuttal, the first speaker in the Custom Components track, Axel Jensen, came right out swinging and hit all the major points. The second speaker, Ben Clinkenbeard, co-author of flexmdi, echoed some of Axel’s points and dove deeper. And so on through the day.

Overall, I’m impressed by the increased technical depth of the presentations in this conference, as compared to last year in Seattle. A lot more code is shown and discussed. I take away some interesting code samples: one from Axel on extending class Panel to add custom children to its header, another from Doug Knudsen on the practical use of Event.preventDefault() for filtering text input, and more.

Another, more subtle step in a positive direction is a growing awareness that there are many ways to get things done, but only a few that may be considered “best practices.” Ben C. hits this chord most often. He mentions the lack of a recommended coding pattern for adding default styles to a custom component. And then he says something that really resonates with my Allurent developer soul, to the effect that frameworks, such as Cairngorm, are just conventions - consistent approaches to some problem, not necessarily ideal solutions to all.

Two more days to look forward to….

“Bitmaps In Flex” is about using some advanced ActionScript APIs to achieve visual effects in a Flex application that are both useful and cool. It assumes the audience is familiar with the the basic use of the Flex Image component and the use of bitmaps in styling, and goes a step beyond, by exploring the ActionScript Bitmap API and its application in Flex. The material to be presented is essential to developing an application that is about imagery: illustration, data visualization, medical imagery, scientific imagery, and so forth. The material also points the way to enhancing the visual impact of any application, by accessing effects that don’t come right out of the Flex box.

This talk dives deep into the Bitmap API, showing what can be accomplished and how. It swoops over best practices for creating custom Flex components, as related to bitmaps. It stops briefly at several sample mini-applications along the way. If you’re a “show me the code” type, you’ll be happy to know that the composition of the presentation is 60% code review, 40% slides.

Neither of the “obvious” approaches works, due to limitations of the Flex 2.0 MXMLC compiler. These approaches are:

1. Define the property with a set function and a get function. Declare the get function public, but keep the set function private. Add [Bindable] metadata.
2. Define the property with a get function but no set function. Add [Bindable] metadata to the get function.

Approach #1 does not work because declaring a get/set function pair with different levels of permission results in a compiler error. The compiler just can’t handle it.

Approach #2 also fails due to compiler limitation. If the metadata reads simply [Bindable], then for some reason the compiler assumes that the property is constant and does not attempt to handle change events for that property. Therefore, bindings involving the property simply don’t work. The compiler does issue a warning to this effect, but the compilation succeeds.
The workaround is simple. Take approach #2, but list the name of the change event for the property in the metadata, lke this:

[Bindable(”somethingChanged”)]

or this:

[Bindable(name=”somethingChanged”)]

I’ve written a little test application that illustrates this approach. The source module “PropertyPatterns.as” is usable as a template for defining bindable properties.
Click here to see the test application

To get the source code, right-click on the test application to bring up a menu, and select one of the “Show source” items from the menu.

This year, I’m planning to present on “Bitmaps in Flex”. This talk is about using some of the best features of the Flash Player in combination with the power of Flex to create animated, visually striking graphical presentations. It goes beyond what can be achieved using simply Flex Effects and styles. Some of the topics I’m planning to cover include:

• What a bitmap-enhanced display can do for the user
• Comparison with Flash timeline: pros and cons
• Bitmap, BitmapData, Loader, Image APIs
• Embedding bitmaps
• Scaling and skewing
• Merging and dissolving
• Creating custom components using bitmaps
• Animation tactics
• A little about Papervision 3D

I’m hoping to make this a fun, interesting talk with wide appeal. If you’re coming from the Flash world, it will show you how to “do it the Flex way” using ActionScript and MXML. If you’re coming from the non-Flash world, it may open your eyes to the possibilities of the powerful graphics engine that underlies Flex.

What about Practical Patterns? If you’re looking for a follow-up to my presentation of last year, please hold that thought. Joe and I decided to put this topic aside for now. It has been only a few months since its last run at MAX 2007, and we feel it could benefit from some more time spent in practice. The next time one of us returns to Patterns, it will be from the point of view of additional experience. If you have thoughts about what should go into the next run of this talk, I’d love to hear them.

See you at the show.