ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Handling events
Listener function defined outside of a class
The following code creates a simple SWF file that displays a red square shape. A listener function named
clickHandler(), which is not part of a class, listens for mouse click events on the red square.
package
{
import flash.display.Sprite;
}
public class ClickExample extends Sprite
{
public function ClickExample()
{
var child:ChildSprite = new ChildSprite();
addChild(child);
}
}
import flash.display.Sprite;
import flash.events.MouseEvent;
class ChildSprite extends Sprite
{
public function ChildSprite()
{
graphics.beginFill(0xFF0000);
graphics.drawRect(0,0,100,100);
graphics.endFill();
addEventListener(MouseEvent.CLICK, clickHandler);
}
}
function clickHandler(event:MouseEvent):void
{
trace("clickHandler detected an event of type: " + event.type);
trace("the this keyword refers to: " + this);
}
When a user interacts with the resulting SWF file by clicking on the square, Flash Player or AIR generates the following
trace output:
clickHandler detected an event of type: click
the this keyword refers to: [object global]
Notice that the event object is passed as an argument to clickHandler(). This allows your listener function to
examine the event object. In this example, you use the event object's type property to ascertain that the event is a click
event.
The example also checks the value of the this keyword. In this case, this represents the global object, which makes
sense because the function is defined outside of any custom class or object.
Listener function defined as a class method
The following example is identical to the previous example that defines the ClickExample class except that the
clickHandler() function is defined as a method of the ChildSprite class:
Last updated 6/6/2012
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