Setting the vertical scroll position on a Spark List control in Flex 4

By Peter deHaan On May 30, 2009 · 12 Comments

The following example shows how you can set the vertical scroll position on a Spark List control in Flex 4 by setting the verticalScrollPosition property on the VerticalLayout object.

The following example(s) require Flash Player 10 and the Adobe Flex 4 SDK. To download the Adobe Flash Builder 4 trial, see http://www.adobe.com/products/flex/. To download the latest nightly build of the Flex 4 SDK, see http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4.
For more information on getting started with Flex 4 and Flash Builder 4, see the official Adobe Flex Team blog.

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/05/30/setting-the-vertical-scroll-position-on-a-spark-list-control-in-flex-4/ -->
<s:Application name="Spark_List_layout_VerticalLayout_verticalScrollPosition_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
    <s:controlBarContent>
        <mx:Form styleName="plain">
            <mx:FormItem label="verticalScrollPosition:">
                <s:HSlider id="slider" />
            </mx:FormItem>
        </mx:Form>
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;
 
            protected function list_creationCompleteHandler(evt:FlexEvent):void {
                slider.maximum = list.dataGroup.contentHeight - list.height;
            }
        ]]>
    </fx:Script>
 
    <s:List id="list"
            horizontalCenter="0"
            verticalCenter="0"
            creationComplete="list_creationCompleteHandler(event);">
        <s:layout>
            <s:VerticalLayout horizontalAlign="justify" 
                    requestedRowCount="4"
                    verticalScrollPosition="{slider.value}" />
        </s:layout>
        <s:dataProvider>
            <s:ArrayList>
                <fx:String>The</fx:String>
                <fx:String>Quick</fx:String>
                <fx:String>Brown</fx:String>
                <fx:String>Fox</fx:String>
                <fx:String>Jumps</fx:String>
                <fx:String>Over</fx:String>
                <fx:String>The</fx:String>
                <fx:String>Lazy</fx:String>
                <fx:String>Dog</fx:String>
            </s:ArrayList>
        </s:dataProvider>
    </s:List>
 
</s:Application>

View source is enabled in the following example.

You can also set the verticalScrollPosition property using ActionScript, as seen in the following example:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/05/30/setting-the-vertical-scroll-position-on-a-spark-list-control-in-flex-4/ -->
<s:Application name="Spark_List_layout_VerticalLayout_verticalScrollPosition_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
    <s:controlBarContent>
        <mx:Form styleName="plain">
            <mx:FormItem label="verticalScrollPosition:">
                <s:HSlider id="slider"
                        change="slider_changeHandler(event)" />
            </mx:FormItem>
        </mx:Form>
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;
 
            protected function list_creationCompleteHandler(evt:FlexEvent):void {
                slider.maximum = list.dataGroup.contentHeight - list.height;
            }
 
            protected function slider_changeHandler(evt:Event):void {
                list.layout.verticalScrollPosition = slider.value;
            }
        ]]>
    </fx:Script>
 
    <s:List id="list"
            horizontalCenter="0"
            verticalCenter="0"
            creationComplete="list_creationCompleteHandler(event);">
        <s:layout>
            <s:VerticalLayout horizontalAlign="justify" 
                    requestedRowCount="4" />
        </s:layout>
        <s:dataProvider>
            <s:ArrayList>
                <fx:String>The</fx:String>
                <fx:String>Quick</fx:String>
                <fx:String>Brown</fx:String>
                <fx:String>Fox</fx:String>
                <fx:String>Jumps</fx:String>
                <fx:String>Over</fx:String>
                <fx:String>The</fx:String>
                <fx:String>Lazy</fx:String>
                <fx:String>Dog</fx:String>
            </s:ArrayList>
        </s:dataProvider>
    </s:List>
 
</s:Application>

This entry is based on a beta version of the Flex 4 SDK and therefore is very likely to change as development of the Flex SDK continues. The API can (and will) change causing examples to possibly not compile in newer versions of the Flex 4 SDK.

About The Author

Peter deHaan

Peter deHaan currently works for Adobe on the Flex SDK QA team. While not working on Flex, Flash, and ColdFusion applications, Peter enjoys making up bios and writing in 3rd person. Peter's rarely updated blog can be found at blogs.adobe.com/pdehaan/, actionscriptexamples.com, airexamples.com, and coldfusionexamples.com.

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12 Responses to Setting the vertical scroll position on a Spark List control in Flex 4

Raul Riera says:

June 1, 2009 at 11:56 pm

I am missing the output :( but thanks anyway…

Also, you might want to change the “warning” message at the beginning to Flash Builder Beta at Labs, It would be easier for people

Reply
arten says:

September 25, 2009 at 7:54 am

I have a question about this :)

It does indeed work, if you have a simple list like this, but it doesn’t work when you add a skinclass to that list…
Do you have any idea why? In the skinclass i just have a datagroup with an itemrenderer.

I also tried putting a scroller around the datagroup (to have a viewport i guess) but that doesn’t work either …
Could you please mail me some feedback?

Thanks a lot!
Maarten

Reply
- Peter deHaan says:
  
  September 25, 2009 at 8:08 am
  
  @Maarten,
  
  Can you file a bug at http://bugs.adobe.com/flex/ and include your test case (and custom skin class) and somebody can investigate.
  
  Thanks,
  Peter
  
  Reply
firsoff says:

January 25, 2010 at 3:53 am

Hi!
[list.contentHeight] not work in the Flash Builder4 Beta 2

Reply
- Peter deHaan says:
  
  January 25, 2010 at 8:16 am
  
  @firsoff,
  
  Try downloading a newer Nightly Flex 4.0 build from http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4
  
  Peter
  
  Reply
  - JabbyPanda says:
    
    February 18, 2010 at 9:22 am
    
    “list.contentHeight” is gone from Flex 4 SDK, I am on Flex 4.0.14173 SDK.
    
    Also checked the beta documentation here:
    http://help.adobe.com/en_US/FlashPlatform//reference/actionscript/3/spark/components/List.html#propertySummary
  - Peter deHaan says:
    
    February 27, 2010 at 1:19 pm
    
    @JabbyPanda,
    
    Good catch, thanks. I believe that list.contentHeight was replaced with list.dataGroup.contentHeight. I updated the example above.
    
    Peter
Adnan Doric says:

March 24, 2010 at 7:59 am

When I scroll to the max using the slider, I still can scroll using the scroll bar, why it doesn’t scroll to the max ?

Reply
marc says:

September 30, 2010 at 1:27 am

today that was useful to me. Thanks!

Reply
Sachin dev tripathi says:

February 15, 2011 at 2:26 am

List.ensureIndexIsVisible() methods is a better option.. You can use it with callLater.

Reply
jag says:

August 25, 2011 at 10:40 am

hi,
i want to control a canvas scroll with d hslider.say,i have 12 date choosers inside a canvas in vertical layout.but i want to show three date choosers at one time as i scroll along.say the slider min val is 0 and max val is 1 with snap interval 0.25.so when i reach 0.25 i want to show first 3 date choosers,when i reach 0.5,then next three and so on..

Reply
Tahir Alvi says:

January 30, 2012 at 1:08 am

Hi,

can we change the vertical scroll bar position from right to left?

Reply