Introduction

What is Adobe Flex? Like Flash, Flex creates SWF files that are rendered by Flash Player. However, Flex is primarily a developer's tool and the way you develop Flex applications is entirely different than the way you develop Flash RIAs. All Flex development is based upon a framework that provides you with reusable and extendable UI components, data retrieval services, event handling functionality and much more. You can create RIAs in a familiar code-centric environment, but you still reap the benefits of Flash applications, which include:

• The ability to design and implement human-centered user interfaces without worrying about browser limitations.
• A runtime environment with almost 100% deployment to all Internet users.
• The powerful ActionScript programming language.
• The ability to integrate rich media like streaming video and sound.

In comparison, the Adobe Flash Authoring environment revolves around a timeline metaphor and visual development tools. Because of this emphasis, and despite the evolution of Flash's programming language, ActionScript, into a fully object-oriented ECMA-4-compliant language, Flash has traditionally been seen as a designer's tool for creating animations. Over the years, many programmers have learned the benefits of using Flash to create powerful RIAs, but others have found the IDE to be difficult to understand.

You should note that Flash and Flex can work together. As a matter of fact, Flex can work directly with other products in the Adobe Create Suite, as well. Designers and programmers can easily "create" in their own environments and then integrate their work to establish an entirely new breed of RIAs.

Who should use Flex?

Flex is geared towards programmers, rather than designers. The primary Flex programming language, ActionScript 3, is object-oriented so it is a good idea for you to have some experience with OOP concepts.

What do I need to buy?

Building Flex applications can be free. All you need is the free, open source Flex SDK, which includes:

• The Flex Framework - the predefined class libraries and application services
• The standalone compiler

The Adobe Flex technologies that cost money are:

• Flex Builder - The Eclipse-based IDE which includes the Flex SDK and other development tools like a debugger and visual designer.
• Flex Charting - A library of interactive charting components that can be bound to data from your Flex applications.
• LiveCycle Data Services (previously Flex Data Services) - The enterprise technology with built-in data management services, Flex-Ajax bridge, Java Message Service (JMS) adapter, and real-time collaboration tools.

How do I build Flex applications?

Once you have decided whether you will use the free Flex SDK or the Flex Builder IDE, you can start your RIA development.

You will use the following two languages:

• MXML is an XML-based markup language that is primarily used to layout application display elements.
• ActionScript is an ECMAScript-compliant object-oriented programming language that is primarily used for application logic.

If you are using the Free SDK, you will use the standalone compiler to compile your code into a SWF file. Flex Builder can be set to compile your code automatically and also create the necessary browser detection and other relevant client-side code.

During compilation, your MXML code is translated into ActionScript code and then all the ActionScript code is compiled into binary SWF files. The SWF file can be uploaded to the web server, where it is then served up based on user request.