<fx:Declarations> tag implemented by the compiler

You use the <fx:Declarations> tag to declare non-default, non-visual properties of the current class. For example, you define effects, validators, and formatters in the body of the <fx:Declarations> tag.

MXML Syntax

The <fx:Declarations> tag has the following syntax:

    <fx:Declarations> 
        <!-- Non-visual declarations. -->
    </fx:Declarations>
            

For example, to apply an effect, you first define it in the <fx:Declarations> tag, and then invoke the effect by calling the Effect.play() method, as the following example shows:

    <?xml version="1.0"?>
    <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
        xmlns:mx="library://ns.adobe.com/flex/mx" 
        xmlns:s="library://ns.adobe.com/flex/spark"">
        <s:layout>
            <s:VerticalLayout/>
        </s:layout>

         <fx:Declarations>
            <s:Resize id="myResizeEffect" 
                target="{myImage}"
                widthBy="10" heightBy="10"/>
        </fx:Declarations>
    
        <mx:Image id="myImage" 
            source="@Embed(source='assets/logo.jpg')"/>
        <s:Button label="Resize Me" 
            click="myResizeEffect.end();myResizeEffect.play();"/>
    </s:Application>