lib/photo_view_screen.dart

import 'package:flutter/material.dart';

class PhotoViewScreen extends StatefulWidget {
  const PhotoViewScreen({
    Key? key,
    required this.imageURL,
    // 引数から画像のURL一覧を受け取る
    required this.imageList,
  }) : super(key: key);

  final String imageURL;
  final List<String> imageList;

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

class _PhotoViewScreenState extends State<PhotoViewScreen> {
  late PageController _controller;

  @override
  void initState() {
    super.initState();
    
    // 受け取った画像一覧から、ページ番号を特定
    final int initialPage = widget.imageList.indexOf(widget.imageURL);

    _controller = PageController(
      initialPage: initialPage,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // ...
      body: Stack(
        children: [
          PageView(
            // ...
            // 受け取った画像一覧を表示
            children: widget.imageList.map((String imageURL) {
              return Image.network(
                imageURL,
                fit: BoxFit.cover,
              );
            }).toList(),
          ),
          // ...
        ],
      ),
    );
  }
}