Macromedia flex 2-migrating applications to flex 2 Manual De Usuario

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Events

About events

The following list is a general overview of the changes to the Event model. Review all event 
handling in your Flex application by using these guidelines.

■

All event objects are either of type Event or a subclass of Event. You should explicitly 
declare or cast them to their appropriate type.

■

Use static constants such as 

MouseEvent.CLICK

 instead of string literals for the event 

type, such as “

click

”. For more information, see 

.

■

Do not use object event listeners. Instead use function listeners. For more information, see 

■

Scoping in event listeners is improved. You no longer need to pass a Delegate to maintain 
scope.

■

Use the 

currentTarget

 property instead of the 

target

 property when you access the 

object that is listening for the event. The 

target

 property refers to the object that 

dispatched the event.

Subclasses of Event, such as MouseEvent, have all the properties of the Event object and 
properties that are specific to that type of event. Choosing the most specific type possible 
provides the following benefits:

■

Faster run-time performance

■

Compile-time type-checking

■

Access to event-specific properties

■

Smaller SWF file size

Component startup life cycle

The ordering of events during a component’s initialization has changed. The 

initialize

 

event is now named 

preinitialize

. 

The 

initialize

 event now occurs after children are added to the component. As a result, 

instead of calling an event handler for the 

creationComplete

 event, you can use the 

initialize

 event handler to perform most initialization tasks. You typically call 

creationComplete

 when you have to wait until the LayoutManager has processed the 

children so that the 

x

, 

y

, 

width

, and 

height

 properties are known.

The 

childrenCreated

 event has been removed. You should use the 

initialize

 event 

instead.

A new event, 

applicationComplete

, has been added. This event is the last one dispatched 

when an application starts up.