User Guide

Using listeners to handle events 69

Using listener functions

Unlike the handleEvent syntax, several listener functions can handle different events. So

instead of having the

if and else if checks in myHandler, you can just define

myChangeHandler for the change event and myScrollHandler for the scroll event and

myList.addEventListener("change", myChangeHandler);

myList.addEventListener("scroll", myScrollHandler);

To use a listener function, you must first define a function:

function myFunction:Function(evtObj:Object){

// your code here

}

Then you call the addEventListener() method from the component instance that

broadcasts the event. The

addEventListener() method takes two parameters: a string

indicating the name of the event and a reference to the function.

componentInstance.addEventListener("eventName", myFunction);

You can call addEventListener() from any component instance; it is included in every UI

component from the EventDispatcher class. For more information, see

EventDispatcher.addEventListener().

For information about the events a component broadcasts, see each component’s entry in the

Components Language Reference.

TIP

The evtObj parameter is an object that is automatically generated when an event is

triggered and passed to the function. The event object has properties that contain

information about the event. For details, see “About the event object” on page 77.