ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Display programming
Manipulating display objects
Flash Player 9 and later, Adobe AIR 1.0 and later
Regardless of which display object you choose to use, there are a number of manipulations that all display objects have
in common as elements that are displayed on the screen. For example, they can all be positioned on the screen, moved
forward or backward in the stacking order of display objects, scaled, rotated, and so forth. Because all display objects
inherit this functionality from their common base class (DisplayObject), this functionality behaves the same whether
you’re manipulating a TextField instance, a Video instance, a Shape instance, or any other display object. The
following sections detail several of these common display object manipulations.
Changing position
Flash Player 9 and later, Adobe AIR 1.0 and later
The most basic manipulation to any display object is positioning it on the screen. To set a display object’s position,
change the object’s x and y properties.
myShape.x = 17;
myShape.y = 212;
The display object positioning system treats the Stage as a Cartesian coordinate system (the common grid system with
a horizontal x axis and vertical y axis). The origin of the coordinate system (the 0,0 coordinate where the x and y axes
meet) is at the top-left corner of the Stage. From there, x values are positive going right and negative going left, while
(in contrast to typical graphing systems) y values are positive going down and negative going up. For example, the
previous lines of code move the object myShape to the x coordinate 17 (17 pixels to the right of the origin) and y
coordinate 212 (212 pixels below the origin).
By default, when a display object is created using ActionScript, the x and y properties are both set to 0, placing the
object at the top-left corner of its parent content.
Changing position relative to the Stage
It’s important to remember that the x and y properties always refer to the position of the display object relative to the
0,0 coordinate of its parent display object’s axes. So for a Shape instance (such as a circle) contained inside a Sprite
instance, setting the Shape object’s x and y properties to 0 will place the circle at the top-left corner of the Sprite, which
is not necessarily the top-left corner of the Stage. To position an object relative to the global Stage coordinates, you can
use the globalToLocal() method of any display object to convert coordinates from global (Stage) coordinates to local
(display object container) coordinates, like this:
Last updated 6/6/2012
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