var lastIndex = 0

func scrollPager(scrollPager: ScrollPager, changedIndex: Int) {
    print("scrollPager index changed: \(changedIndex)")
    lastIndex = changedIndex
}

override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
    coordinator.animate(alongsideTransition: nil) { _ in
            
        self.scrollPager.setSelectedIndex(index: self.lastIndex, animated: false)
    }
}