ViewPagerAndroid#onPageScroll

Executed when transitioning between pages (ether because of animation for the requested page change or when user is swiping/dragging between pages) The event.nativeEvent object for this callback will carry following data: - position - index of first page from the left that is currently visible - offset - value from range [0,1) describing stage between page transitions. Value x means that (1 - x) fraction of the page at "position" index is visible, and x fraction of the next page is visible.