The ViewStack change event is fired when the selected child container is changed. You should be able to use it.
I'm aware of the change event, but when the component is the first time activated, the component will be crated just on selection so will the change event fire after first initialization or before, further in case of after display update (e.g. 2nd time selected) is this the same?
If the views are instanciated on selection, the change event will probably be fired before the creationComplete event of the child view.
One solution, if the views under the viewstack are not that heavy, would be to set the ViewStack creationPolicy to all, to avoid any instanciation problem.
Another solution would be to listen for the creationComplete event of the ViewStack children. You can prevent using the change event until the creationComplete event has been fired on the concerned child, and use the creationComplete event instead for the first time the view is showed.