Expanded Branch不会在Flex Tree中第一次展示它的孩子？

I have added an event handler for itemOpening event for the tree component inside the handler basically ido myTree.selectedItem = event.item ; and then add the new data inside myTree.selectedItem.children.push(newData); But It do not show simultaneously instead I have to close , open the branch again to see the new data . I think I need to refresh something after adding new data but dont know what ? below is the code but without the declaration , script tag etcI have added an event handler for itemOpening e