Flutter PageView with different page size

pageview_adaptive.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: PageviewGallery(),
    );
  }
}


class PageviewGallery extends StatefulWidget {
  @override
  _PageviewGalleryState createState() => _PageviewGalleryState();
}

class _PageviewGalleryState extends State<PageviewGallery> {
  final PageController ctrl = PageController(
    viewportFraction: 0.55,
  );

  int currentPage = 0;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      body: PageView.builder(
          controller: ctrl,
          itemCount: 8,
          physics: const BouncingScrollPhysics(),
          itemBuilder: (context, int index) {
            // Active page
            bool active = index == currentPage;
            return _buildStoryPage(active);
          }),
    ));
  }

  @override
  void initState() {
    super.initState();
    ctrl.addListener(() {
      int pos = ctrl.page!.round();
      if (currentPage != pos) {
        {
          setState(() {
            currentPage = pos;
          });
        }
      }
    });
  }
}

_buildStoryPage( bool active) {
  // Animated Properties
  final double blur = active ? 30 : 0;
  final double offset = active ? 20 : 0;
  final double top = active ? 100 : 200;

  return AnimatedContainer(
    duration: Duration(milliseconds: 500),
    curve: Curves.easeOutQuint,
    margin: EdgeInsets.only(top: top, bottom: 50, right: 30),
    decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(20),
        color :Colors.red,
        boxShadow: [BoxShadow(color: Colors.black87, blurRadius: blur, offset: Offset(offset, offset))]),
  );
}