MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur télécharger pdf (Page 112)

112 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 “Using static constants” on page 114.

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

“Using function listeners” on page 115.

■ 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.

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MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur Page 112