There are two properties to mention here itemDoubleClick , doubleClickEnabled . In itemDoubleClick property call a function with event like the below
and in secound property doubleClickEnabled=”true”
Now write some code to expand the tree on click of node in the function.
private function tree_itemDoubleClick(evt:ListEvent):void — here as u can see the event is ListEvent and u have import events package
in the function
var node:XML = treeID.selectedItem as XML; — this will get the node
var isOpen:Boolean = treeID.isItemOpen(node); — this will check tree is opened or not
treeID.expandItem(node, !isOpen); — this will expand the tree if not and close if opened (viceversa)
Now on double of tree node that respected node will expand.