I modified the tabs sample so that nav bar appears only when in the chat-details. I did this by removing ion-nav-bar element in the index.html.
In the browser, the change looks as expected where the content in other views are to the top and in the chat details the nav-bar shows up shifting the content down.
In the android emulator, there is a visual gap at the top for all the views and nav bar shows up in the chat-details view. Any suggestion on how to make the behavior same as browser?