MACROMEDIA FLASH 8-COMPONENTS LANGUAGE Reference page 783

Description
Event; broadcast to all registered listeners when the selected index of the list changes as a result
of user interaction.
The first usage example uses a dispatcher/listener event model. A component instance
( ) dispatches an event (in this case, ) and the event is handled by a
listInstance change
function, also called a handler, on a listener object ( ) that you create. You
listenerObject
define a method with the same name as the event on the listener object; the method is called
when the event is triggered. When the event is triggered, it automatically passes an event
object ( ) to the listener object method. Each event object has properties that
eventObject
contain information about the event. You can use these properties to write code that handles
the event. For more information, see "EventDispatcher class (API)" on page 500.
Finally, you call the method on the component instance that
addEventListener()
broadcasts the event to register the listener with the instance. When the instance dispatches
the event, the listener is called.
The second usage example uses an handler and must be attached directly to a List
on()
instance. The keyword , used inside an handler attached to a component, refers to
this on()
the component instance. For example, the following code, attached to the List instance
, sends "_level0.my_list" to the Output panel:
my_list
on (change) {
trace(this);
}
Example
The following example adds three items to the List component. Changing the selected value
of the list causes the value of the newly selected item to be displayed in the Output panel. To
try this code, drag a List component to the Stage and give it the instance name my_list. Add
the following code to Frame 1 in the timeline:
var my_list:mx.controls.List;
my_list.addItem({data:'flash', label:'Flash'});
my_list.addItem({data:'dreamweaver', label:'Dreanweaver'});
my_list.addItem({data:'coldfusion', label:'ColdFusion'});
// Create listener object.
var listListener:Object = new Object();
listListener.change = function(evt_obj:Object) {
trace("Value changed to: " + evt_obj.target.value);
}
// Add listener.
my_list.addEventListener("change", listListener);
List.change 779