Learning ActionScript 3.0

Chapter 4. THE DISPLAY LIST

One of the most dramatic changes introduced by ActionScript 3.0, particularly for designers accustomed to prior versions of ActionScript, is the way in which visual elements are added to an application at runtime. In prior versions of ActionScript, a separate approach was used to add most kinds of visual assets at runtime, requiring varied syntax. Management of those assets—particularly depth management—and creating and destroying objects, were also fairly restrictive and could be relatively involved depending on what you were trying to accomplish.

ActionScript 3.0 brings with it an entirely new way of handling visual assets. It’s called the display list. It’s a hierarchical list of all visual elements in your file. It includes common objects such as movie clips, but also objects such as shapes and sprites that either didn’t previously exist or could not be created programmatically.

In this chapter, we’ll look at the following topics:

• The Sum of Its Parts. Understanding the display list means understanding its parts. In addition to knowing the kinds of objects that can be part of the display list, it’s also important to grasp the simple difference between display objects and display object containers.

• Adding and Removing Children. The best part of the display list is how easy and consistent it is to add objects to, and remove objects from, the list.

• Managing Object Names, Positions, and Data Types. In addition to adding and removing display objects, you will ...