flutter_webview_pluginでiOSのassetsへのURLを教えてください

前提・実現したいこと

flutter_webview_pluginを使用して、assets内のhtmlを表示しようとしています。
Androidでは「file:///android_asset/flutter_assets/assets/top.html」でアクセスできます。
iOSだとおそらくassetsへのURLが異なるため表示されませんでした。

###質問
Androidでの「file:///android_asset/flutter_assets/assets/top.html」は、iOSではどのようなURLになるのでしょうか？

発生している問題・エラーメッセージ

エラーメッセージはなく、ただ空白のページが表示されます。

該当のソースコード

assetsはプロジェクトフォルダ直下に配置しています。

project_app
 |-assets
     |-top.html

pubspec.yaml

yaml
1...
2dependencies:
3  flutter:
4    sdk: flutter
5
6
7  # The following adds the Cupertino Icons font to your application.
8  # Use with the CupertinoIcons class for iOS style icons.
9  cupertino_icons: ^1.0.2
10  flutter_webview_plugin: ^0.4.0
11
12dev_dependencies:
13  flutter_test:
14    sdk: flutter
15
16# For information on the generic Dart part of this file, see the
17# following page: https://dart.dev/tools/pub/pubspec
18
19# The following section is specific to Flutter.
20flutter:
21
22  # The following line ensures that the Material Icons font is
23  # included with your application, so that you can use the icons in
24  # the material Icons class.
25  uses-material-design: true
26
27  # To add assets to your application, add an assets section, like this:
28  # assets:
29  #   - images/a_dot_burr.jpeg
30  #   - images/a_dot_ham.jpeg
31  assets:
32      - assets/
33...

main.dart

dart
1import 'package:flutter/material.dart';
2import 'package:flutter_webview_plugin/flutter_webview_plugin.dart';
3
4String selectedUrl = 'file:///android_asset/flutter_assets/assets/top.html';
5// ignore: prefer_collection_literals
6final Set<JavascriptChannel> jsChannels = [
7  JavascriptChannel(
8      name: 'Print',
9      onMessageReceived: (JavascriptMessage message) {
10        print(message.message);
11      }),
12].toSet();
13
14void main() async {
15  WidgetsFlutterBinding.ensureInitialized();
16  runApp(MyApp());
17}
18
19class MyApp extends StatelessWidget {
20  final flutterWebViewPlugin = FlutterWebviewPlugin();
21
22  @override
23  Widget build(BuildContext context) {
24    return MaterialApp(
25      title: 'Flutter WebView Demo',
26      theme: ThemeData(
27        primarySwatch: Colors.blue,
28      ),
29      routes: {
30        '/': (_) {
31          return WebviewScaffold(
32            url: selectedUrl,
33            javascriptChannels: jsChannels,
34            mediaPlaybackRequiresUserGesture: false,
35            appBar: AppBar(
36              title: const Text('Widget WebView'),
37            ),
38            // withZoom: true,
39            withLocalStorage: true,
40            withLocalUrl: true,
41            allowFileURLs: true,
42            localUrlScope: selectedUrl,
43          );
44        },
45      },
46    );
47  }
48}

top.html

html
1<!doctype html>
2<html lang="en">
3
4<head>
5    <meta charset="UTF-8" />
6    <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=0" />
7    <title>test</title>
8    <script type="text/javascript">
9        const CONTENT_PATH = "file:///android_asset/flutter_assets/assets/"
10    </script>
11    <script type="text/javascript" src="js/lib/phaser.js"></script>
12    <script type="text/javascript" src="js/lib/phaser.min.js"></script>
13</head>
14
15<body>
16    <div>
17        <script>
18        console.log(Phaser);
19        </script>
20    </div>
21</body>
22
23</html>