ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with movie clips
The Scene class has several properties that give information about a scene. The labels property returns an array of
FrameLabel objects representing the frame labels in that scene. The name property returns the scene’s name as a string.
The numFrames property returns an int representing the total number of frames in the scene.
Creating MovieClip objects with ActionScript
Flash Player 9 and later, Adobe AIR 1.0 and later
One way of adding content to the screen in Flash is by dragging assets from the library onto the Stage, but that is not
the only workflow. For complex projects, experienced developers commonly prefer to create movie clips
programatically. This approach brings several advantages: easier re-use of code, faster compile-time speed, and more
sophisticated modifications that are available only to ActionScript.
The display list API of ActionScript 3.0 streamlines the process of dynamically creating MovieClip objects. The ability
to instantiate a MovieClip instance directly, separate from the process of adding it to the display list, provides flexibility
and simplicity without sacrificing control.
In ActionScript 3.0, when you create a movie clip (or any other display object) instance programatically, it is not visible
on the screen until it is added to the display list by calling the addChild() or the addChildAt() method on a display
object container. This allows you to create a movie clip, set its properties, and even call methods before it is rendered
to the screen. For more information on working with the display list, see “Working with display object containers” on
page 159.
Exporting library symbols for ActionScript
Flash Player 9 and later, Adobe AIR 1.0 and later
By default, instances of movie clip symbols in a Flash document’s library cannot be dynamically created (that is,
created using only ActionScript). This is because each symbol that is exported for use in ActionScript adds to the size
of your SWF file, and it’s recognized that some symbols might not be intended for use on the stage. For this reason, in
order to make a symbol available in ActionScript, you must specify that the symbol should be exported for
ActionScript.
To export a symbol for ActionScript:
1 Select the symbol in the Library panel and open its Symbol Properties dialog box.
2 If necessary, activate the Advanced settings.
3 In the Linkage section, activate the Export for ActionScript checkbox.
This will activate the Class and Base Class fields.
By default, the Class field is populated with the symbol name, with spaces removed (for example, a symbol named
“Tree House” would become “TreeHouse”). To specify that the symbol should use a custom class for its behavior,
enter the full name of the class including its package in this field. If you want to be able to create instances of the
symbol in ActionScript, but don’t need to add any additional behavior, you can leave the class name as-is.
The Base Class field’s value defaults to flash.display.MovieClip. If you want your symbol to extend the
functionality of another customer class, you can specify that class’s name instead, as long as that class extends the
Sprite (or MovieClip) class.
4 Press the OK button to save the changes.
Last updated 6/6/2012
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