Query widget doesn't render the filter result

I have configured a Query widget on map service, filter by "category".
It can do a query, get result in the query widget. But it cannot render the result set on a graphics layer

I check the sample, it renders the filter result on the map.
http://resources.arcgis.com/en/help/...nfig-query.xml

My Query Widget xml file. What i missed to render the result on map? Thanks.
<?xml version="1.0" ?>
<configuration>
<layer>http://testserver/arcgis/rest/services/Testing/TestReportAll/MapServer/0</layer>
<query>1=1</query>
<titlefield>category</titlefield>
<linkfield/>
<refreshrate/>
<zoomscale>50000</zoomscale>
<shareresults>true</shareresults>
<orderbyfields>event_number</orderbyfields>
<fields all="false">
<field name="event_number" alias="occ_number"/>
<field name="category" alias="category"/>
</fields>
<filterfield>
<name>category</name>
<alias>Filter by category #</alias>
</filterfield>
</configuration>