Chapter 21: Eventdispatcher Class; Event Objects - MACROMEDIA FLASH 8-COMPONENTS LANGUAGE Reference

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CHAPTER 21
EventDispatcher class
Events let your application know when the user has interacted with a component, and when
important changes have occurred in the appearance or life cycle of a component—such as its
creation, destruction, or resizing.
The methods of the EventDispatcher class let you add and remove event listeners so that your
code can react to events appropriately. For example, you use the
method to register a listener with a component
EventDispatcher.addEventListener()
instance. The listener is invoked when a component's event is triggered.
If you want to write a custom object that emits events that aren't related to the user interface,
EventDispatcher is smaller and faster to use as a mix-in for UIComponent than
UIEventDispatcher.

Event objects

An event object is passed to a listener as a parameter. The event object is an ActionScript
object that has properties that contain information about the event that occurred. You can use
the event object inside the listener callback function to access the name of the event that was
broadcast, or the instance name of the component that broadcast the event. For example, the
following code uses the property of the event object to access the
target evtObj label
property of the instance and send the value to the Output panel:
myButton
listener = new Object();
listener.click = function(evtObj){
trace("The " + evtObj.target.label + " button was clicked");
}
myButton.addEventListener("click", listener);
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