main.dart

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

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

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

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: AspectRatio(
          aspectRatio: 2.0,
          child: PageView(
            controller: PageController(
              initialPage: 1,
              viewportFraction: 0.6,
            ),
            children: [
              ColoredBox(color: Colors.red),
              ColoredBox(color: Colors.green),
              ColoredBox(color: Colors.blue),
            ],
          ),
        ),
      ),
    );
  }
}

class ColoredBox extends StatelessWidget {
  final Color color;

  const ColoredBox({Key? key, required this.color}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      color: color,
      margin: EdgeInsets.all(24),
    );
  }
}