ActionScript 3.0 Programming: Overview, Getting Started, and Examples of New Concepts

Jumping into Display Programming

For those of you who have worked with ActionScript in the past, chances are you've used it to dynamically manipulate elements on the stage. The term display programming refers to ActionScript 3.0's ability to work with different elements that appear on the stage. To effectively do so, you need to know something about ActionScript 3.0's display structure.

The first thing to know is that the Stage is the base container of the display structure. As you add further containers to the stage, they are added to a display list. Each container can hold different display objects that appear on the screen. To get started, you'll see how to create an object container (DisplayObjectContainer object) that's placed on the stage, and then you'll place a Shape object into a container.

If you've had previous experience with Flash, you know that you can place objects such as text fields, drawings, and even other movie clips into a MovieClip object. However, ActionScript 3.0 has a new Sprite class that can hold other objects in a similar way as the MovieClip class. Unlike the MovieClip class, though, the Sprite class has no timeline. (In fact, the MovieClip is actually a subclass of the Sprite class.) Without a timeline, the Sprite class requires less memory and can be used as an ideal container for different objects while retaining many of the advantages of a MovieClip object.

Take a look at Figure 3. It shows the script that created the square that appears on the stage ...