AdvancedDatagrid headerRenderer advanced question :-)

Question

Hello, it;s really hard to explain my problem, but I will try
anyway
I have just one AdvancedDataGrid (imagine only one column)
with a custom headerRenderer, which is just a Label, nothing more.
The headerRenderer is actually a ClassFactory object which craeates
that Label by calling newInstance() method, whenever Flex needs to
create that Label object for the header, this is all clear.
And my question is: when Flex calls the newInstance() and
what Flex would do with the old Label object, when he creates a new
instance?
I am asking, because when I create this simple application,
nothing special, Flex creates 2 Label objects for the header
renderer. I know it because I put the 'trace' function into that
Label. So whenever Datagrid redraws, I can see that there are two
Label objects, both the same (the same header text), but only one
is visible. I think, that the first Label is obsolete, because the
second Label was created by newInstance() method, but the first one
is still there, was not deleted nor removed from container (it was
just moved into a AdvancedDataGridListContentHolder).
So, both Labels are active, when datagrid redraws, both
Labels updates, but just one is visible. so my question is why Flex
creates two labels??
Thanks, just for reading :-)

Answer 1

I have even problem. But i create CheckBoxes.
Here is how i implement CheckBox in my Column
<mx:DataGridColumn dataField="maxDamage" headerText="100%
Damage" editable="false">
<mx:itemRenderer>
<myComp:CheckBoxRenderer/>
</mx:itemRenderer>
</mx:DataGridColumn>
And this is my CheckBoxRenderer:
import mx.controls.CheckBox;
import mx.controls.DataGrid;
import mx.controls.dataGridClasses.DataGridColumn;
import mx.core.IFactory;
import mx.events.CollectionEvent;
import mx.events.FlexEvent;
public class CheckBoxRenderer implements IFactory
public function newInstance():*
var checkBox:CheckBox = new CheckBox();
checkBox.addEventListener(Event.CHANGE, onChange);
checkBox.addEventListener(FlexEvent.CREATION_COMPLETE,
onCreationComplete);
return checkBox;
private function onChange(event:Event):void
var checkBox:CheckBox = event.target as CheckBox;
if (checkBox == null) return;
var dataGrid:DataGrid = checkBox.owner as DataGrid;
// Field by data objects that must be midified
var dataField:String =
(dataGrid.columns[checkBox.listData.columnIndex] as
DataGridColumn).dataField;
checkBox.data[dataField] = checkBox.selected;
dataGrid.dataProvider.dispatchEvent(new
CollectionEvent(CollectionEvent.COLLECTION_CHANGE));
private function onCreationComplete(event:FlexEvent):void
var checkBox:CheckBox = event.target as CheckBox;
if (checkBox == null) return;
var grid:DataGrid = checkBox.owner as DataGrid;
if (grid == null) return;
var dataField:String =
(grid.columns[checkBox.listData.columnIndex] as
DataGridColumn).dataField;
if (dataField == null) return;
checkBox.selected = checkBox.data[dataField];
checkBox.dispatchEvent(new Event(Event.CHANGE));
Can anybody tell me, how must write my CheckBoxRenderer to
haven't unvisible itemRenderers?
With unvisible itemRenderer i have problem with checkboxes
and they render unright...