opacityRoute method
Implementation
PageRoute opacityRoute(Widget page, RouteSettings settings) {
return PageRouteBuilder(
settings: settings,
pageBuilder: (_, __, ___) => page,
transitionDuration: const Duration(milliseconds: 300),
transitionsBuilder: (_, o, ___, c) => FadeTransition(
opacity: o,
child: c,
),
);
}