Doesn’t seem like normal behaviour for DataGrid!

I ran into a problem the other day trying to create a DataGrid that had voting buttons as an itemRenderer. When an action was taken in that cell, the buttons would change, i.e., gray out or light up to show a click occurred. The problem that would happen is that, when I scrolled the list up or down, that column would randomize!

I found posts that talked about solutions for very simple things like a checkbox in a column that did not have any elaborate actionscript behind it, but not to address a component that sat behind the itemRenderer. I figured it out though, and the answer is pretty simple.

I had to add a dataChange function call in the component’s main tag so it would force the cell to rethink it’s status when the grid would scroll.

The main mxml:

<mx:DataGrid id="userGrid" dataProvider="{userData}" sortableColumns="true"
    draggableColumns="false" width="100%" height="100%">
  <mx:columns>
    <mx:DataGridColumn dataField="Topic" width="100" />
    <mx:DataGridColumn id="votecol" dataField="status" headerText="Vote" sortable="true"
        itemRenderer="castVote" width="120" />
    </mx:columns>
</mx:DataGrid>

The castVote component:

<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" xmlns="*" dataChange="gridMoved()"
    width="100%" height="100%">
<mx:Script>
        <![CDATA[
        import mx.core.Application;
        import mx.events.ListEvent;

        private var myStatus:int = 0;

        private function gridMoved():void{
                if (data != null) {
                        myStatus=data.status;
                }
                doShow(myStatus);
        }

        private function doShow(n:int):void {
                // 0 means already voted, 1 is for, 2 is against
                if (n==0) {
                        buttons.visible=true;
                        v1.visible = v2.visible = false;
                        return;
                }else if (n==1) {
                        v1.visible=true; v2.visible=false;
                        myStatus = n;
                        buttons.visible=false;
                }else if (n==2) {
                        v2.visible=true; v1.visible=false;
                        myStatus = n;
                        buttons.visible=false;
                }
        }

        private function doClick(n:int):void {
                data.status = myStatus = n;
                doShow(n);
        }

        ]]>
</mx:Script>

        <mx:Label id="v1" text="You voted FOR this resolution" visible="false" />
        <mx:Label id="v2" text="You voted AGAINST this resolution!" visible="false" />
        <mx:HBox id="buttons">
                <mx:Button label="YES" click="doClick(1);" />
                <mx:Button label="NO" click="doClick(2);" />
        </mx:HBox>

</mx:Canvas>