fade_page_route.dart

import 'package:flutter/widgets.dart';

class FadePageRoute extends PageRouteBuilder {
  final Widget widget;

  FadePageRoute({this.widget})
      : super(
          pageBuilder: (
            BuildContext context,
            Animation<double> animation,
            Animation<double> secondaryAnimation,
          ) {
            return widget;
          },
          transitionsBuilder: ((
            BuildContext context,
            Animation<double> animation,
            Animation<double> secondaryAnimation,
            Widget child,
          ) {
            return FadeTransition(
              opacity: Tween(begin: 0.0, end: 1.0).animate(animation),
              child: child,
            );
          }),
        );
}