Error when extending AdvancedDataGridRenderer

I have set the itemrenderer package like that:

package myrenderers { import mx.controls.advancedDataGridClasses.AdvancedDataGridItemRenderer;

public class theHeaderRenderer extends AdvancedDataGridItemRenderer
{
    public function theHeaderRenderer()
    {
        super();
        setStyle("verticalAlign","middle"); 
    }
}

}

However when I include the following lines in my AdvancedDataGridColumn tag,

            <fx:Component>
                <myrenderers:theHeaderRenderer"/>
            </fx:Component>

        </mx:headerRenderer>

            <fx:Component>
                <renderers:someotherrenderer/>
            </fx:Component>

        </mx:itemRenderer>

I get the following error:

TypeError: Error #1034: Type Coercion failed: cannot convert mx.controls.dataGridClasses::DataGridListData@ac84f81 to mx.controls.advancedDataGridClasses.AdvancedDataGridListData. at mx.controls.advancedDataGridClasses::AdvancedDataGridItemRenderer/set listData()[E:\dev\4.x\frameworks\projects\datavisualization\src\mx\controls\advancedDataGridClasses\AdvancedDataGridItemRenderer.as:232] at mx.controls::DataGrid/http://www.adobe.com/2006/flex/mx/internal::calculateHeaderHeight()[E:\dev\4.x\frameworks\projects\framework\src\mx\controls\DataGrid.开发者_JAVA技巧as:2182] at mx.controls.dataGridClasses::DataGridHeader/measure()[E:\dev\4.x\frameworks\projects\framework\src\mx\controls\dataGridClasses\DataGridHeader.as:201] at mx.core::UIComponent/measureSizes()[E:\dev\4.x\frameworks\projects\framework\src\mx\core\UIComponent.as:8216] at mx.core::UIComponent/validateSize()[E:\dev\4.x\frameworks\projects\framework\src\mx\core\UIComponent.as:8140] at mx.managers::LayoutManager/validateSize()[E:\dev\4.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:617] at mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:709] at mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1072]

Can anyone suggest how I can come across this problem?

Thank you

First, I'd recommend you extend your custom headerRenderer from AdvancedDataGridHeaderRenderer instead of AdvancedDataGridItemRenderer.

Second, it looks like you are mixing the mx:DataGrid with the mx:AdvancedDataGrid. I guess that's the cause for your type coercion error. Make sure that your MXML looks something like this:

<mx:AdvancedDataGrid>
    <mx:columns>
        <mx:AdvancedDataGridColumn dataField="foo" headerRenderer="myrenderers.theHeaderRenderer"/>
    </mx:columns>
</mx:AdvancedDataGrid>