MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manual de usuario descargar pdf (Pagina 113)

Migrating the Event object 113

Migrating the Event object

This section describes migration issues related to accessing the Event object.

Using the Event object

The Event object is no longer of type Object. It is now of type flash.events.Event. Specify a

stricter type in functions, as follows:

private function eventHandler(event:Object):Void { // Flex 1.5

private function eventHandler(event:Event):void { // Flex 2

You should also now cast the event.target in an event handler to an appropriate type to

avoid compile-time warnings. The new code should specify the stricter event type as a

function parameter, as the following example shows:

private function doDragExit(event:DragEvent):void {

event.target.hideDropFeedback(event);

}

If you assign the target to a stronger-typed variable, you must cast; for example:

var clickTarget:Button = Button(event.target);

When using the Event object, you are encouraged to use the most strict type possible. This

lets you access properties that are specific to the target type. For example, in a mouse click

listener, you should declare the Event of type MouseEvent rather than of type Event, as

follows:

private function myClickHandler(event:MouseEvent):void { ... }

If you use Event as the type, rather than MouseEvent, you do not have access to any properties

that are specific to the MouseEvent class.

Using the target property

Calling methods and accessing properties on the target can be confusing. The default type of

Event.target is Object. Because ActionScript is strongly typed, you can call

event.target.methodName() only if you cast the event.target to an object type that

defines that

methodName. The same applies for properties. You can access

event.target.property only if you define property on the new type.

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MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manual de usuario Pagina 113