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Flex – Event Handling

This chapter describes the usage of Event Handling:

lex uses concept of event to pass data from one object to another depend upon the state or user

interaction within the application.

ActionScript has a generic Event class which defines much of the functionality needed to work with events. Every

time an event occurs within a Flex application, three types of objects from the Event class hiearchy are created.

Event has the following three key properties

Property

Description

type

type states about what kind of event just happened. This may be click, initialize, mouseover,

change, etc. The actual values will be represented by constants like MouseEvent.CLICK.

target

The target property of Event is an object reference to the component that generated the

event.If you click a Button with an id of clickMeButton, the target of that click event will be

clickMeButton

currentTarget

The currentTarget property varies container hiearchy. It mainly deals with flow of events.

Event Flow Phases

An event goes through three phases looking for event handlers.

Phase

Description

Capture

In the capture phase the program will start looking for event handlers from the outside (or top)

parent to the innermost one. The capture phase stops at the parent of the object that triggered the

event.

Target

In the target phase ,the component that triggered the event, is checked for an event handler.

Bubble

The Bubble phase is reverse of capture phase, working back through the structure, from the target

component's parent on up.

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MACROMEDIA FLEX-FLEX ACTIONSCRIPT LANGUAGE Manuale Utente Pagina 86