Why is sortCompareFunction called when clicking checkbox on non-sortable column?

Question

Hello,
I have a datagrid that contains three static DataGridColumn columns.  The first column uses a checkbox item renderer whose sortable property is set to false:
<mx:DataGridColumn
width="100"
sortable="false"
itemRenderer="com.mycomponent.CheckBoxItemRenderer" />
On creation complete, a fourth column is added dynamically to the datagrid, through ActionScript, and several of its properties are set, like so:
var dgc : DataGridColumn = new DataGridColumn();
dgc.headerText = someAttribute.name;
dgc.itemRenderer = new ClassFactory(ProductResultItemRenderer);
dgc.sortCompareFunction = attributeCompareFunction;
Everything is rendered just fine.  If I sort the datagrid items by clicking the column header of the second or third columns (these are the static columns that use Flex's default sort function) and then click on any of the items' checkboxes, there are no issues.  However, if I sort the items by clicking on the header of the dynamically-added fourth column and then click on any of the items' checkboxes, the results are partially re-sorted.  Setting a breakpoint in my attributeCompareFunction method, any time I click a checkbox in this use case, this compare function is called.
Can someone shed some light on why this function is invoked in this last use case, especially when performing a non-sortable event (clicking on a checkbox)?
Thanks,
-Jose

Answer 1

Hi Alex,
I set a breakpoint in the sortCompareFunction, but I'm unable to determine what is calling it.  Here is the call stack:
Main Thread (Suspended)
Function/<anonymous>
mx.collections::SortField/http://www.adobe.com/2006/flex/mx/internal::internalCompare
mx.collections::Sort/internalCompare
mx.collections::Sort/findItem
mx.collections::ListCollectionView/http://www.adobe.com/2006/flex/mx/internal::findItem
mx.collections::ListCollectionView/addItemsToView
mx.collections::ListCollectionView/moveItemInView
mx.collections::ListCollectionView/handlePropertyChangeEvents
mx.collections::ListCollectionView/listChangeHandler
flash.events::EventDispatcher/dispatchEventFunction [no source]
flash.events::EventDispatcher/dispatchEvent [no source]
mx.collections::ArrayList/internalDispatchEvent
mx.collections::ArrayList/itemUpdateHandler
flash.events::EventDispatcher/dispatchEventFunction [no source]
flash.events::EventDispatcher/dispatchEvent [no source]
com.my.package.models::ProductVO/dispatchEvent [no source]
com.my.package.models::ProductVO/set compare [no source]
com.my.package.components::CheckBoxItemRenderer/onChange
com.my.package.components::CheckBoxItemRenderer/___CheckBoxItemRenderer_CheckBox1_change
flash.events::EventDispatcher/dispatchEventFunction [no source]
flash.events::EventDispatcher/dispatchEvent [no source]
mx.core::UIComponent/dispatchEvent
spark.components.supportClasses::ToggleButtonBase/buttonReleased
spark.components.supportClasses::ButtonBase/mouseEventHandler
The event dispatched by "ProductVO/dispatchEvent" is of type "mx.events.PropertyChangeEvent", which is OK since the "compare" property was updated.  However, later in the call stack, the "ArrayList" object fires an "internalDispatchEvent" of type "mx.events.CollectionEvent", which is an "update" event.  Looking at the rest of the call stack, this is the event that leads to the re-sort.
Is there any way to prevent this CollectionEvent event from firing and, if so, how?
Thanks,
-Jose