As of iOS 7.0, all views automatically go behind navigation bars, toolbars and tab bars to provide what Apple calls "context" – having some idea of what's underneath the UI (albeit blurred out with a frosted glass effect) gives users an idea of what else is just off screen.
If this is getting in your way (and honestly it does get in the way surprisingly often) you can easily disable it for a given view controller by modifying its edgesForExtendedLayout property.
For example, if you don't want a view controller to go behind any bars, use this:
edgesForExtendedLayout = []
for your case you can use it like this:
yourvc.edgesForExtendedLayout = []
For your reference i am also attaching a link which also answers your question.