Programming Flex 3

Chapter 5. Framework Fundamentals

When you build a Flex application, you create an .swf file. Users can then run the application using Flash Player, just as they would any other .swf file that was created by any other means (e.g., by using the Flash authoring tool). Flex .swf files have two distinct characteristics:

• When building Flex applications, the developer has access to and uses a vast library of ActionScript classes known as the Flex framework. The parts of the framework the developer uses are compiled into the resultant .swf file.

• At runtime, the Flex framework code that is compiled into the .swf dictates a particular way in which the application will load, initialize, and run.

The Flex framework has been designed in such a way that it “just works” without you, the developer, needing to know too much about it. Yet, having a better understanding of the inner workings of the Flex framework will aid you in many ways. For example, the Flex framework provides built-in preloading functionality, and it uses a default progress indicator (unless you tell it otherwise). That means you get these capabilities for free, and they will work without any extra effort on your part. However, you can also customize the progress indicator, as well as customize what happens while the application is downloading and/or initializing, to suit your needs. Without a better understanding of the Flex framework, customizing Flex in this way may be difficult. This is also true of other scenarios, including ...