How to Maintain Open Nodes On a Flex Grouping Collection - actionscript-3

Question

I have a Flex Application that has a Advanced Data Grid that contains a Grouping Collection. I want the screen to initially have all the nodes closed. From there the user can choose to open one or two and view the information within. If the click on one of the Nodes Children it changes the View using a view stack to a screen containing More info on that child. However when we return to the initial screen it returns with all nodes closed again.
I would like the App to remember what nodes were left open and what the last clicked item was and have it highlighted.
I have tried using IHierarchicalCollectionView(dataProviderName).openNodes and assigning it to an Object when the view changes and when it returns Assisning this object to IHierarchicalCollectionView(dataProviderName).openNodes. But the app seems to go into a loop and IE stops responding.
This is the Code for my DataGrid as it stands. Any help would be appreciated.
public class SummaryGridBase extends AdvancedDataGrid
{
[Bindable]
protected var _modelLocator:ModelLocator = ModelLocator.getInstance();
[Bindable]
override public function set dataProvider(value:Object):void
{
super.dataProvider = value;
}
override protected function collectionChangeHandler(event:Event):void
{
super.collectionChangeHandler(event);
trace("Summary Grid Trace 1");
if( event is CollectionEvent && (event as CollectionEvent).kind == CollectionEventKind.REFRESH )
{
trace("Summary Grid Trace 2");
this.validateGridAndExpand();
}
}
private function validateGridAndExpand():void
{
this.validateNow();
var rootLevel:ArrayCollection = ModelLocator.getInstance().groupingCollection.getRoot() as ArrayCollection;
for each( var item:Object in rootLevel )
{
this.expandItem( item, true, false );
}
}
protected function changeHandler(event:ListEvent):void
{
trace("Change in Summary Data Selection" +(this.selectedItem.Business));
if( this.selectedItem.Business == null )
{
trace("Im Null");
Alert.show( "Please Expand a Vendor Using The Arrow Beside it \nand Select a Polymer From the List", 'Warning', mx.controls.Alert.OK);
}
else
{
var summaryEvent:SummaryEvent = new SummaryEvent( SummaryEvent.SELECT_SUMMARY, (this.selectedItem.Business as String), (this.selectedItem.Op_Site as String),(this.selectedItem.Vendor as String),(this.selectedItem.Item_Desc as String) );
summaryEvent.dispatch();
}
}
public function SummaryGridBase()
{
super();
}
}

Answer 1

I just stumbled across this question and had encountered the same problem recently. I know its late but for the sake of the internet this is what worked for me.
I (eventually) found the answer here
So there's was two parts, first where the data is updated you first get the hierarchical view of what nodes are open and restore this after the grouping collection has been updated:
var hierarchical:IHierarchicalCollectionView = advDatagrid.dataProvider as IHierarchicalCollectionView;
var openNodes:Object = hierarchical.openNodes;
grpCollection.refresh();
advDatagrid.dataProvider = grpCollection;
advDatagrid.validateNow();
IHierarchicalCollectionView(advDatagrid.dataProvider).openNodes = openNodes;
But the other part was to set a grouping object function.
So in your grouping definition:
<mx:GroupingCollection2 id="grpCollection" source="{data}">
<mx:Grouping groupingObjectFunction="grpObjFunc">
<mx:GroupingField name="name"/>
</mx:Grouping>
And a simple function to return a unique id:
private function grpObjFunc(value:String):Object
{
return {uid:value};
}