Modale

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Page(),
    );
  }
}

class SlideTopRoute extends PageRouteBuilder {
  final Widget widget;
  SlideTopRoute({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 SlideTransition(
            position: Tween<Offset>(
              begin: const Offset(0.0, 1.0),
              end: Offset.zero,
            ).animate(animation),
            child: child,
          );
        });
}

class SlideBotomRoute extends PageRouteBuilder {
  final Widget enterPage;
  final Widget exitPage;
  SlideBotomRoute({this.exitPage, this.enterPage})
      : super(
          pageBuilder: (
            BuildContext context,
            Animation<double> animation,
            Animation<double> secondaryAnimation,
          ) =>
              enterPage,
          transitionsBuilder: (
            BuildContext context,
            Animation<double> animation,
            Animation<double> secondaryAnimation,
            Widget child,
          ) =>
              Stack(
            children: <Widget>[
              SlideTransition(
                position: Tween<Offset>(
                  begin: Offset.zero,
                  end: Offset.zero,
                ).animate(animation),
                child: enterPage,
              ),
              SlideTransition(
                position: Tween<Offset>(
                  begin: Offset.zero,
                  end: const Offset(0.0, 1.0),
                ).animate(animation),
                child: exitPage,
              ),
            ],
          ),
        );
}

class Page extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () {
            Navigator.push(context, SlideTopRoute(widget: ModalPage()));
          },
          child: Text('Launch Modal'),
        ),
      ),
    );
  }
}

class ModalPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Modal Page'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: () {
            final Route<SecondaryPage> secondaryRoute = MaterialPageRoute(
              settings: RouteSettings(name: 'Secondary'),
              builder: (BuildContext context) => SecondaryPage(),
            );
            Navigator.push(context, secondaryRoute);
          },
          child: Text('Launch Secondary Page'),
        ),
      ),
    );
  }
}

class SecondaryPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Secondary Page')),
      body: Center(
        child: RaisedButton(
          onPressed: () {
            Navigator.pushAndRemoveUntil(
                context,
                SlideBotomRoute(exitPage: this, enterPage: Page()),
                ModalRoute.withName('/'));
          },
          child: Text('Clear All'),
        ),
      ),
    );
  }
}