ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Display programming
Advantages of the display list approach
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 3.0, there are separate classes for different types of display objects. In ActionScript 1.0 and 2.0, many
of the same types of objects are all included in one class: the MovieClip class.
This individualization of classes and the hierarchical structure of display lists have the following benefits:
More efficient rendering and reduced memory usage
Improved depth management
Full traversal of the display list
Off-list display objects
Easier subclassing of display objects
More efficient rendering and smaller file sizes
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 1.0 and 2.0, you could draw shapes only in a MovieClip object. In ActionScript 3.0, there are simpler
display object classes in which you can draw shapes. Because these ActionScript 3.0 display object classes do not
include the full set of methods and properties that a MovieClip object includes, they are less taxing on memory and
processor resources.
For example, each MovieClip object includes properties for the timeline of the movie clip, whereas a Shape object does
not. The properties for managing the timeline can use a lot of memory and processor resources. In ActionScript 3.0,
using the Shape object results in better performance. The Shape object has less overhead than the more complex
MovieClip object. Flash Player and AIR do not need to manage unused MovieClip properties, which improves speed
and reduces the memory footprint the object uses.
Improved depth management
Flash Player 9 and later, Adobe AIR 1.0 and later
In ActionScript 1.0 and 2.0, depth was managed through a linear depth management scheme and methods such as
getNextHighestDepth().
ActionScript 3.0 includes the DisplayObjectContainer class, which has more convenient methods and properties for
managing the depth of display objects.
In ActionScript 3.0, when you move a display object to a new position in the child list of a DisplayObjectContainer
instance, the other children in the display object container are repositioned automatically and assigned appropriate
child index positions in the display object container.
Also, in ActionScript 3.0 it is always possible to discover all of the child objects of any display object container. Every
DisplayObjectContainer instance has a numChildren property, which lists the number of children in the display object
container. And since the child list of a display object container is always an indexed list, you can examine every object
in the list from index position 0 through the last index position (numChildren - 1). This was not possible with the
methods and properties of a MovieClip object in ActionScript 1.0 and 2.0.
Last updated 6/6/2012
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