Flash® Builder™ 4 and Flex® 4 Bible

Chapter 4. Understanding the Anatomy of a Flex Application

IN THIS CHAPTER

• Using Flex programming languages

• Understanding MXML and FXG

• Understanding XML syntax

• Using Flex 4 XML namespaces

• Creating application containership with MXML

• Understanding ActionScript 3

• Combining MXML and ActionScript

• Using the MXML and ActionScript editors in Flash Builder 4

• Using the new Spark Application component

In this chapter, I describe the basic architecture of a Flex application from the point of view of a developer. In previous chapters, I described the role of Adobe Flash Player in hosting a Flex application at runtime, regardless of whether you use the version of Flash Player that's hosted by a Web browser (a Web application) or the version that's embedded in Adobe AIR (a desktop application).

In either case, Flash Player "plays" the application with a bit of software known as the ActionScript Virtual Machine (AVM). Flash Player 10 (the version that runs Flex 4 applications) includes two versions of the AVM. The first is for older documents and applications built in Flash and Flex 1.x that use ActionScript 1 and 2. The other, newer AVM is for documents and applications that use ActionScript 3.

Note

Flash Player versions 9 and 10 can run either ActionScript 2 or ActionScript 3, but not both simultaneously. A Flash component built with ActionScript 2 that's incorporated into an application built in Flex 2 or higher has its ActionScript code ignored by the Flash Player at runtime.

Flash Player is doing the work ...