MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur télécharger pdf (Page 16)

16 Getting Started

Step 4: Update events

The Event model changed in Flex 2. However, you can migrate most event handlers with

minimal effort. This section describes the most popular changes that you must make to your

event handling code. For more information about migrating events, see Chapter 6, “Events,”

on page 111.

Specify types

Events are now more strongly typed than in Flex 1.x. As a result, you should specify the object

type in the event listener function. For example, previously you could write the following:

function myListener(event) { var s = event.type; }

Now, you must specify an event object in the function’s signature; for example:

private function myListener(event:Event):void { var s = event.type; }

Where possible, make the events as specific as possible. If the previous example was a listener

for click events, specify a MouseEvent as the type:

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

Dispatch custom events

When you dispatch custom events, you must declare a new Event object rather than use a

generic object; for example:

click="dispatchEvent(new Event('checkOut'))"

Remove delegates

You are no longer required to wrap a listener function with a Delegate to maintain application

scope. You can remove the Delegate from the following line:

b1.addEventListener("click", mx.utils.Delegate.create(this,myListener));

So the line appears as follows:

b1.addEventListener(MouseEvent.CLICK, myListener);

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MACROMEDIA FLEX 2-MIGRATING APPLICATIONS TO FLEX 2 Manuel d'utilisateur Page 16