private async Task TransitionBackward( AlternativePage currentPage, AlternativePage newPage, ContentPresenter previousPagePresenter, ContentPresenter newPagePresenter) { var transition = currentPage != null ? (currentPage.PageTransition ?? this.PageTransition) : this.PageTransition; if (transition != null) { if (currentPage != null) { await currentPage.OnTransitioningFromInternal(); } if (newPage != null) { await newPage.OnTransitioningToInternal(); } await transition.TransitionBackward(previousPagePresenter, newPagePresenter); if (currentPage != null) { await currentPage.OnTransitionedFromInternal(); } if (newPage != null) { await newPage.OnTransitionedToInternal(); } } }