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
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.
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 ...