problem about ArcGIS API for Flex3.0

[galechaung]

I tried to use the samples of ArcGIS offical website in my flash builder4.5,but the map does not show up.
The source code is below. Help me!!!!
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:esri="http://www.esri.com/2008/ags"
pageTitle="World Topographic Map">
<!--
This sample shows how to add a topographic basemap layer to your application.

The sample uses a cached map service from ArcGIS Online.

You can browse the ArcGIS.com site for additional online basemap and reference
map services or publish your own geographic data as a service using ArcGIS Server.
-->

<fx:Declarations>
<esri:Extent id="initialExtent"
xmin="-13635000" ymin="4541000" xmax="-13625000" ymax="4547000">
<esri:SpatialReference wkid="102100"/>
</esri:Extent>
</fx:Declarations>

<esri:Map extent="{initialExtent}">
<esri:ArcGISTiledMapServiceLayer url="http://server.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer"/>
</esri:Map>
</s:Application>

[IvanBespalov]

Hi,
are you sure that you have fulfilled all the tips listed here?

Some useful links:
Build Your First Flex 4.5 Application.
Adobe developer center.
Flex in a Week video training.

[KenBuja · Accepted solution]

Also, the Flex 3.0 API requires the Adobe Flex 4.6 SDK or higher, which in turn requires at least Flash Player 11.1.

[galechaung]

My problem is solved by using the Adobe Flex 4.6 SDK.
Thank you very much!!!

[KenBuja]

You're welcome. Please remember to click the Mark as Answer check.