This is my code. When i clicked the tab vicemap and then the tab mainmap at the bottom of the screen, the ionnavbar just disappeared. what have i done wrong?
I found that someone suffered the same problem. Ion-nav-bar invisible inside modal
I have decided to use ionheadbar instead of this ionnavbar. i struggled several days for this ionnavbar stuff 
. it looks like that ionheadbar can work also fine. http://codepen.io/anon/pen/WvZgJb
Fine. It’s an old bug. I used the new js file and it works fine.