Setting bordercontainer backgroundimage from inside component

For my flex project I am making, I'm trying to change the background of my website change to the image I have clicked on. The background in my main page I have set like this:

<s:BorderContainer id="backgroundContainer" width="100%" height="100%" backgroundImage="@Embed('assets/background.png')" borderAlpha="0">

        <s:layout>
            <s:VerticalLayout horizontalAlign="center"/>
        </s:layout>


    <mx:LinkBar styleName="mainnav" width="600" dataProvider="content" horizontalCenter="0" paddingLeft="20" paddingTop="125"/>

    <s:Image top="5" bottom="5" horizontalCenter="50" source="assets/nav.png"/>

    <mx:ViewStack id="content">

        <mx:HBox id="home"
                 label="Home">
            <component:home/>
        </mx:HBox>

        <mx:HBox id="bio"
                 label="Bio">
            <component:bio/>
        </mx:HBox>

        <mx:HBox id="portfolio"
                 label="Portfolio">
            <component:portfolio/>
        </mx:HBox>

        <mx:HBox id="contact"
                 label="Contact">
            <component:contact/>
        </mx:HBox>

    </mx:ViewStack>     

    </s:BorderContainer>

Now from inside my component, I am trying to set the the background of the image you click on.

<fx:Script>
    <![CDATA[               
        import mx.core.Application;


    public function changeBackground(event:MouseEvent):void
    {
        Application.application.backgroundContainer.setStyle('backgroundImage', img1.source);
    }
    ]]>

</fx:Script>

I call this function when you click on an image.

<mx:Image id="img1" source="assets/placeholder.jpg" click="changeBackground(event)"/>

But it doesn't work. So I was wondering how this should be done?

Thank you, Thomas

you can use BitmapFill and declare all your backgrounds first. Also, be sure your changeBackground function is public in your main application since it will be called from a component.

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" 
    xmlns:mx="library://ns.adobe.com/flex/mx" xmlns:component="component.*">

    <fx:Script>
        <![CDATA[

            public function changeBackground(bitmapFillObj:BitmapFill):void
            {
                backgroundContainer.backgroundFill = bitmapFillObj;
            }

        ]]>
    </fx:Script>

    <fx:Declarations>
        <s:BitmapFill id="_bg1" source="@Embed('assets/bg1.jpg')"/>
        <s:BitmapFill id="_bg2" source="@Embed('assets/bg2.jpg')"/>
    </fx:Declarations>

    <s:BorderContainer id="backgroundContainer" width="100%" height="100%" backgroundImage="@Embed('assets/bg1.jpg')" borderAlpha="0">

        <component:home/>

    </s:BorderContainer>

</s:WindowedApplication>

And now your component

<fx:Script>
    <![CDATA[
        import mx.core.FlexGlobals;
    ]]>
</fx:Script>

<fx:Declarations>
    <!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>

<s:layout>
    <s:HorizontalLayout/>
</s:layout>

<s:Button label="click to show bg 1" click="FlexGlobals.topLevelApplication.changeBackground(FlexGlobals.topLevelApplication._bg1)"/>

<s:Button label="click to show bg 2" click="FlexGlobals.topLevelApplication.changeBackground(FlexGlobals.topLevelApplication._bg2)"/>

Your just have to adapt the code to your project, clicking on your images instead of buttons. Good luck!