Slideshow

Motivation

You want to have a region of your page that changes images when the user selects a button.

Method

Store a list of links to the slide images in an instance. Use another instance variable to store the state of the images is currently selected. Use a trigger to update the image number.

Link to XForms Application

Load XForms Application

Sample Source Code

<html 
   xmlns="http://www.w3.org/1999/xhtml" 
   xmlns:xf="http://www.w3.org/2002/xforms"
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:ev="http://www.w3.org/2001/xml-events">
    <head>
        <title>Slide Show</title>
        <xf:model id="data-model">
            <xf:instance id="data" xmlns="">
                <links>
                    <link href="http://www.bav-astro.de/sterne/monv838/monv838-hubble-20040304.jpg">Image 1</link>
                    <link href="http://aether.lbl.gov/Images/resizenowmap.jpg">Image 2</link>
                    <link href="http://www.nasa.gov/images/content/143744main_hubble_spiral_2006.jpg">Image 3</link>
                    <link href="http://www.space.gc.ca/asc/img/sci_core-hubble.jpg">Image 4</link>
                </links>
            </xf:instance>
            <xf:bind nodeset="instance('data')/link/@href" type="xs:anyURI"/>
            <xf:instance id="state" xmlns="">
                <state>
                    <cycle>0</cycle>
                </state>
            </xf:instance>
            <xf:action ev:event="cycle-next">
                <xf:setvalue ref="instance('state')/cycle" value="(. + 1) mod 4"/>
                <xf:dispatch name="update-model" target="data-model"/>
            </xf:action>
            <xf:action ev:event="update-model">
                <xf:rebuild/>
                <xf:recalculate/>
                <xf:revalidate/>
                <xf:refresh/>
            </xf:action>
        </xf:model>
    </head>
    <body>
        <xf:trigger>
            <xf:label>Next</xf:label>
            <xf:action ev:event="DOMActivate">
                <xf:dispatch name="cycle-next" target="data-model"/>
            </xf:action>
        </xf:trigger>
        <xf:output ref="instance('state')/cycle"/>) <xf:output ref="instance('data')/link[1 + instance('state')/cycle]"/>
        <br/>
        <xf:output ref="instance('data')/link[1 + instance('state')/cycle]/@href" mediatype="image/*"/>
    </body>
</html>

Discussion

This program has the Next trigger calls the "cycle-next" named event when it is pressed. This event, which is defined in the model, updates the cycle and resets it back to one after the slides are done. After that it instructs the form to recalculate its dependency graph. This updates the visible image.

Note that the output must have a the mediatype set to be image/* for the browser to render the link as an image correctly.

Attribution

This example was created by Chris Wallace and the University of Western England.

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