Flex is a highly productive, free, open source framework for building expressive web applications that deploy consistently on all major browsers, desktops, and operating systems by leveraging the Adobe® Flash® Player and Adobe AIR® runtimes. While Flex applications can be built using only the free Flex SDK, Adobe Flash Builder™ (formerly Adobe Flex® Builder™) software can accelerate development through features like intelligent coding, interactive step-through debugging, and visual design of the user interface layout.

Note: Flex SDK 4.1 has been released which provides support for the Flash Player 10.1 and Adobe AIR 2 runtimes, critical bugfixes as well as the new Layout Mirroring feature.

As a product manager for Flex I’ve talked with many people about the upcoming release of Flex 4, including customers and our own development team, and the level of excitement around this version is higher than any I’ve seen in the past. We are providing releases of the two tools geared towards Flex: Adobe Flash Catalyst (currently in beta) and Adobe Flash Builder 4; but the foundation for it all is the Flex 4 SDK. This article provides an overview of what you’ll encounter as you play with the new SDK and framework.

You may also be interested in reading What’s new in Flash Builder 4 by Andrew Shorten, andDifferences between Flex 3 SDK and Flex 4 SDK by Joan Lafferty.

The work on the Flex SDK has been focused around three primary themes:

• Design in Mind: providing a framework that supports a new degree of expressiveness, easily enabled with tools.
• Developer Productivity: improving compiler performance and adding productivity enhancements to language features like data binding.
• Framework Evolution: taking advantage of new Flash Player capabilities and adding features required by common use-cases