I'm using XLPagerTabStrip in a swift 3 application.
This is my storyboard:
I added CollectionView to VC in Interface Builder, and set its class to "ButtonBarView"
I added top space contrains to ButtonBarView to have space between it and navigationBar but it keep always 0 space
You need make your buttonBarView linked to your ButtonBarPagerTabStripViewController
buttonBarView
Hope this helps