You dispatch the event from your screen when it's ready, such as when assets are done loading.
You can use any event that you want. I'll choose Event.READY
. Pass that constant to the transitionDelayEvent
property when you add your screen to the navigator:
var item:StackScreenNavigatorItem = new StackScreenNavigatorItem(MyScreen);
item.transitionDelayEvent = Event.READY;
Then, when you navigate to MyScreen, the transition will not start on its own, and the old screen will continue being displayed. Once your assets are loaded, or whatever else you need to do is done, you dispatch the event from MyScreen:
dispatchEventWith(Event.READY);
That will start the transition and navigation will continue normally.