Chapter: Internet & World Wide Web HOW TO PROGRAM - Rich Internet Application Client Technologies - Adobe Flex 2 and Rich Internet Applications

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Flex Platform Overview

The Flex platform requires the Flash Player 9 runtime environment.

Flex Platform Overview


The Flex platform requires the Flash Player 9 runtime environment. Flash Player 9 provides the ActionScript Virtual Machine and graphical capabilities that execute Flex applications. Flash Player 9, as described in Chapters 16–17, is a multimedia-rich application environ-ment that runs on most platforms. Flash Player installation is detailed in those chapters, but for end users, only the Flash Player 9 browser plug-in is required. The plug-in, including a debug version, is included as part of the Flex SDK (Software Development Kit) installa-tion. Flex applications are essentially Flash programs that use the Flex framework of user interface elements, web services, animations and more. The Flex development environment is programming-centric in contrast to the animation-centric Flash authoring tool.


In addition to describing user interfaces, MXML can describe web services, data objects, visual effects and more. Flex’s user interface elements are much richer and more consistent than those of HTML and AJAX because they’re rendered the same way on all platforms by the Flash player. The root element of every MXML application is the Appli-cation element (<mx:Application>), inside which all Flex elements reside.


The Flex SDK is a free download, which you can get from ucts/flex/downloads. It includes an MXML compiler and debugger, the Flex frame-work, the user interface components, and some templates and examples. You can extract the zip file anywhere on your computer. The compiler and debugger included with the Flex SDK are command-line utilities. They’re written in Java, so you must have Java Runtime Edition 1.4.2_06 (or later) installed. To check your current version, run java - version in your command line.


ActionScript 3 is Adobe’s object-oriented scripting language. Flash Player 9 uses ver-sion 2 of the ActionScript Virtual Machine (AVM2), which adds support for ActionScript 3 and provides many performance improvements over the previous version. This virtual machine is being submitted as open source to the Mozilla Firefox project to provide sup-port for ActionScript 3 and JavaScript 2. This engine, called Tamarin, is slated to be included in Firefox 4.


ActionScript 3 supports such object-oriented capabilities as inheritance, encapsulation and polymorphism. Also, it uses an asynchronous programming model. This means that the program will continue to execute while another operation is being completed, such as a call to a web service. This ensures that the user interface is responsive even while the appli cation is busy processing data, an important feature of RIAs. In many cases, you’ll need to take advantage of event handling and data binding to handle asynchronous operations.


Flex Builder is Adobe’s graphical IDE for Flex applications. A 30-day free trial is available at It is based on Eclipse, a popular open source IDE. Because Flex Builder costs money, and because you can develop Flex applications without it, we won’t use Flex Builder in this book.


Adobe LiveCycle Data Services ES extends Flex’s built-in data connectivity, allowing for such features as data push and synchronization. It also enables Flex applications to handle disconnection from the server, synchronizing data upon reconnection. The Express edition of Adobe LiveCycle Data Services ES is available for free at  trylivecycle_dataservices/. This version is limited to use on a single server with a single CPU (the license agreement is included with the download).


Flex Charting provides an extensible library of plotting and graphing elements, including pie charts, line graphs, bar graphs, bubble charts and plots. Flex Charting also provides appealing animations for dynamic data representations. Flex Charting is available for purchase from Adobe, and a 30-day free trial is available at flex. An excellent demonstration of Flex Charting is the Flex Charting Sampler available at


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