Macromedia flex 2 Manual

142

Creating Simple Visual Components in ActionScript

Your custom component can also define event listeners within the component itself to handle 
the events internally. For example, 

 

defined event listeners for the 

keyDown

 and 

creationComplete

 events within the body of the 

component. This allows the component to handle those events internally. 

The example used the 

creationComplete

 event to access the default 

fontSize

 property of 

the component. You could not access this property in the constructor itself because Flex does 
not define it until after the component is created. For more information on the initialization 
order of a component, see 

. 

Dispatching custom events

Your ActionScript component can define custom events and use the predefined events. You 
use custom events to support data binding, to respond to user interactions, or to trigger 
actions by your component. For an example that uses events to support data binding, see 

. 

For each custom event dispatched by your component, you must do the following:

1.

Create an 

Event

 object describing the event.

2.

(Optional) use the 

[Event]

 metadata tag to make the event public so that other 

components can listen for it. 

3.

Dispatch the event by using the 

dispatchEvent()

 method.

To add information to the event object, you define a subclass of the flash.events.Event class to 
represent the event object. For more information on creating custom event classes, see 

NO

TE

Even though you define event listeners for the events in the component itself, your 
application can also register listeners for those events. The event listeners defined within 
the component execute before any listeners defined in the application.