I have the following scenario:
Why does it happen and how can I prevent it?
I know a solution is to set the focusEnable to false but this is not what I want.
?I think this will be tricky unless you can designate some other element to receive focus.
You may need to reconsider why you need to set stage.focus = null in step 2.
I found a solution to this. Add an event listener for Event.Activate. When it is triggered I add another event listener for FOCUS_IN for application. Then, if a field will be focused, it will go trigger the activate event and then the focus in. On focus in handler, I remove the focus and also remove the focus in handler.