Creating and Extending Flex 2 Components > Creating Custom Flex Components > Creating Custom Events > About events

About events

Adobe Flex applications are event-driven. Events let an application know when the user interacts with the interface, and also when important changes happen in the appearance or life cycle of a component, such as the creation of a component or its resizing. Events can be generated by user input devices, such as the mouse and keyboard, or by the asynchronous operations, such as the return of a web service call or the firing of a timer.

The core class of the Flex component architecture, mx.core.UIComponent, defines core events, such as updateComplete, resize, move, creationComplete, and others that are fundamental to all components. Subclasses of UIComponent inherit these events.

Custom components that extend existing Flex classes inherit all the events of the base class. Therefore, if you extend the Button class to create the MyButton class, you can use the click event, and the events that all controls inherit, such as mouseOver or initialize, as the following example shows:

<?xml version="1.0"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" xmlns:MyComp="*"> 

    <mx:Script>
        <![CDATA[
            import flash.events.Event;

            // Event listener for the click event. 
            private handleClick(eventObj:Event):void {
                // Define event listener.
            }

            // Event listener for the initialize event. 
            private function handleInit(eventObj:Event):void {
                // Define event listener.
            }

        ]]>
    </mx:Script>

    <MyComp:MyButton 
        click="handleClick(event);" 
        initialize="handleInit(event);" 
/>

</mx:Application>

In addition to using the events inherited from its superclasses, your custom components can define custom events. You use custom events to support data binding, to respond to user interactions, or to trigger actions by your component.

For more information on the Flex event mechanism, see Using Events in Flex 2 Developer's Guide.

Subtopics

Flex 2

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