How to catch the navigator click event

I have a plugin on host object. When the hostA is selected, my plugin view will display a popup windows, while this popup window have a delay, during this time, I could select to hostB, that might cause the popup windows display on the hostB view, because the contextObject is not set to null. (If the selected node from a host navigate to a cluster or VM, the _contextObject would be set to null.)

public function set contextObject(value:Object):void {
      _contextObject = IResourceReference(value);
      if (_contextObject == null) {        
         clearData();
         return;
      }

     requestData();

}

So I want to let hostA view know that now the hostB is selected(Navigated to), and hostA should be deactive, and do not popup the window.

I had try the deactive event, but it did not work.

Which event should I use or listen to? Or is there any good way to do this? My plugin is now base on Flex, but not html5.