Flutter realizes the gradual enlargement of hero pictures and the equal proportion method of pictures. Pictures are smoothly enlarged

Picture list page

floatingActionButton: FloatingActionButton(
        child: Icon(Icons.pool),
        onPressed: () {
          // iOS -> Modal The way 
//          Navigator.of(context).push(MaterialPageRoute(
//            builder: (ctx) {
//              return HYModalPage();
//            },
//            fullscreenDialog: true
//          ));
          Navigator.of(context).push(PageRouteBuilder(
            transitionDuration: Duration(seconds: 3),
            pageBuilder: (ctx, animation1, animation2) {
              return FadeTransition(
                opacity: animation1,
                child: HYModalPage(),
              );
            }
          ));
//          Navigator.of(context).pushNamed(routeName)
        },
      )

Picture details page

import 'package:flutter/material.dart';

class HYImageDetailPage extends StatelessWidget {
  final String _imageURL;

  HYImageDetailPage(this._imageURL);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      body: Center(
        child: GestureDetector(
            onTap: () {
              Navigator.of(context).pop();
            },
            child: Hero(tag: _imageURL, child: Image.network(_imageURL))
        ),
      ),
    );
  }
}