ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Display programming
In ActionScript 3.0, you can easily traverse the display list sequentially; there are no gaps in the index numbers of a
child list of a display object container. Traversing the display list and managing the depth of objects is much easier than
was possible in ActionScript 1.0 and 2.0. In ActionScript 1.0 and 2.0, a movie clip could contain objects with
intermittent gaps in the depth order, which could make it difficult to traverse the list of object. In ActionScript 3.0,
each child list of a display object container is cached internally as an array, resulting in very fast lookups (by index).
Looping through all children of a display object container is also very fast.
In ActionScript 3.0, you can also access children in a display object container by using the getChildByName() method
of the DisplayObjectContainer class.
Full traversal of the display list
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 1.0 and 2.0, you could not access some objects, such as vector shapes, that were drawn in the Flash
authoring tool. In ActionScript 3.0, you can access all objects on the display list—both those created using ActionScript
and all display objects created in the Flash authoring tool. For details, see “Traversing the display list” on page 163.
Off-list display objects
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 3.0, you can create display objects that are not on the visible display list. These are known as off-list
display objects. A display object is added to the visible display list only when you call the addChild() or
addChildAt() method of a DisplayObjectContainer instance that has already been added to the display list.
You can use off-list display objects to assemble complex display objects, such as those that have multiple display object
containers containing multiple display objects. By keeping display objects off-list, you can assemble complicated
objects without using the processing time to render these display objects. You can then add an off-list display object
to the display list when it is needed. Also, you can move a child of a display object container on and off the display list
and to any desired position in the display list at will.
Easier subclassing of display objects
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 1.0 and 2.0, you would often have to add new MovieClip objects to a SWF file to create basic shapes
or to display bitmaps. In ActionScript 3.0, the DisplayObject class includes many built-in subclasses, including Shape
and Bitmap. Because the classes in ActionScript 3.0 are more specialized for specific types of objects, it is easier to
create basic subclasses of the built-in classes.
For example, in order to draw a circle in ActionScript 2.0, you could create a CustomCircle class that extends the
MovieClip class when an object of the custom class is instantiated. However, that class would also include a number
of properties and methods from the MovieClip class (such as totalFrames) that do not apply to the class. In
ActionScript 3.0, however, you can create a CustomCircle class that extends the Shape object, and as such does not
include the unrelated properties and methods that are contained in the MovieClip class. The following code shows an
example of a CustomCircle class:
Last updated 6/6/2012
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