Unlike Macromedia before them, Adobe has recognised that if Flex is going to successfully compete with Ajax libraries and the forthcoming Microsoft XAML release, it needs to gain significant mind-share as soon as possible. As such, it comes in various flavours from the free version to fairly expensive (in NZ terms).
This is the third major iteration of Flex and so the technology is now well structured, reliable and fast. Also, Flex Builder2 is sensibly licensed per seat so that it is no longer a corporate toy.
The Flex2 documentation set is very extensive; it is split into seven volumes and much of it is in both HTML and PDF format. As PDF documents the information runs to over 3,000 pages, although the 'Getting Started' manual is only 240 pages and probably the only one worth printing out, sitting down and reading from cover to cover.
What is Flex?
First, what is the Flex technology? At its core, it is a rich set of library widgets that can be invoked with a mark-up language MXML (minimal XML) with events that can execute Actionscript commands. These can be compiled with a command-line compiler, to create a SWF file that can be downloaded and run in any browser (rather like HTML really).
The profound difference here is that you are not restricted to the puny HTML widget set and ActionScript is a real programmer's language that runs the same on all browsers that have a Flash plugin. Furthermore, this part of the technology is free. You can download the SDK from the web, print out a few PDF files, fire up Notepad and you're away.
Memorising 3,000 pages of documentation is beyond me, so I prefer a real IDE with context-sensitive help and keyword prompting. This is called Flex Builder2 and it is based on the Eclipse platform. It can be installed stand-alone or as part of an existing Eclipse installation. See Figure 1 for a view of Flex Builder2.
As with all modern development environments, 1280 x 1024 is really the working minimum screen size.
Note in the top right hand corner, the States panel. This allows you to design alternate views for effectively the same data in a different state. So for instance, the cart viewer shown could have a different view state once the order is placed.
There are three aspects to this technology that I find particularly impressive: its deployment reach, the integration of MXML with programming code and the variable binding.
When it comes to reach, in the usual conflict between richness of application and ease of deployment, Flex seems to stand alone in being an excellent development platform that provides more client richness than you normally need and more platform portability than you normally require.
There does still seem to be a gap down at the bottom-end of the market with no support yet on the Flash Lite engine for Flex2 applications, so if the target market is smart phones then Flex2 is probably not the right tool. The UI support libraries are also fairly chunky, varying between about 100kB and 800kB depending on the variety of UI widgets, so anyone wishing to deploy Flex2 applications over dial-up connections will need to put some effort into smart caching and shared libraries.
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