Repository: flutter
Issue: [Flutter WebView] Accessibility not working with Flutter WebView HTML page for both iOS and Android 
Labels: a: accessibility,p: webview,package,team-ecosystem,has reproducible steps,P2,triaged-ecosystem,found in release: 3.22,found in release: 3.24

### Steps to reproduce

1. Use the example App for Flutter WebView[webview_flutter].
2. On building it over the physical device, turn on the accessibility voiceOver/TalkBack.
3. After that try fo focus on the HTML content that we have on different pages.

### Expected results

Talkback should read what we have on screen and also focus on the text and other components, what's inside WebViewWidget.

### Actual results

Talkback is not reading what we have on web view screen, what's inside WebViewWidget

### Code sample

<details open><summary>Code sample</summary>

```dart
// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// ignore_for_file: public_member_api_docs

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:webview_flutter/webview_flutter.dart';
// #docregion platform_imports
// Import for Android features.
import 'package:webview_flutter_android/webview_flutter_android.dart';
// Import for iOS features.
import 'package:webview_flutter_wkwebview/webview_flutter_wkwebview.dart';
// #enddocregion platform_imports

void main() => runApp(const MaterialApp(home: WebViewExample()));

const String kNavigationExamplePage = '''
<!DOCTYPE html><html>
<head><title>Navigation Delegate Example</title></head>
<body>
<p>
The navigation delegate is set to block navigation to the youtube website.
</p>
<ul>
<ul><a href="https://www.youtube.com/">https://www.youtube.com/</a></ul>
<ul><a href="https://www.google.com/">https://www.google.com/</a></ul>
</ul>
</body>
</html>
''';

const String kLocalExamplePage = '''
<!DOCTYPE html>
<html lang="en">
<head>
<title>Load file or HTML string example</title>
</head>
<body>

<h1>Local demo page</h1>
<p>
  This is an example page used to demonstrate how to load a local file or HTML
  string using the <a href="https://pub.dev/packages/webview_flutter">Flutter
  webview</a> plugin.
</p>

</body>
</html>
''';

const String kTransparentBackgroundPage = '''
  <!DOCTYPE html>
  <html>
  <head>
    <title>Transparent background test</title>
  </head>
  <style type="text/css">
    body { background: transparent; margin: 0; padding: 0; }
    #container { position: relative; margin: 0; padding: 0; width: 100vw; height: 100vh; }
    #shape { background: red; width: 200px; height: 200px; margin: 0; padding: 0; position: absolute; top: calc(50% - 100px); left: calc(50% - 100px); }
    p { text-align: center; }
  </style>
  <body>
    <div id="container">
      <p>Transparent background test</p>
      <div id="shape"></div>
    </div>
  </body>
  </html>
''';

const String kLogExamplePage = '''
<!DOCTYPE html>
<html lang="en">
<head>
<title>Load file or HTML string example</title>
</head>
<body onload="console.log('Logging that the page is loading.')">

<h1>Local demo page</h1>
<p>
  This page is used to test the forwarding of console logs to Dart.
</p>

<style>
    .btn-group button {
      padding: 24px; 24px;
      display: block;
      width: 25%;
      margin: 5px 0px 0px 0px;
    }
</style>

<div class="btn-group">
    <button onclick="console.error('This is an error message.')">Error</button>
    <button onclick="console.warn('This is a warning message.')">Warning</button>
    <button onclick="console.info('This is a info message.')">Info</button>
    <button onclick="console.debug('This is a debug message.')">Debug</button>
    <button onclick="console.log('This is a log message.')">Log</button>
</div>

</body>
</html>
''';

class WebViewExample extends StatefulWidget {
  const WebViewExample({super.key});

  @override
  State<WebViewExample> createState() => _WebViewExampleState();
}

class _WebViewExampleState extends State<WebViewExample> {
  late final WebViewController _controller;

  @override
  void initState() {
    super.initState();

    // #docregion platform_features
    late final PlatformWebViewControllerCreationParams params;
    if (WebViewPlatform.instance is WebKitWebViewPlatform) {
      params = WebKitWebViewControllerCreationParams(
        allowsInlineMediaPlayback: true,
        mediaTypesRequiringUserAction: const <PlaybackMediaTypes>{},
      );
    } else {
      params = const PlatformWebViewControllerCreationParams();
    }

    final WebViewController controller =
        WebViewController.fromPlatformCreationParams(params);
    // #enddocregion platform_features

    controller
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..setBackgroundColor(const Color(0x00000000))
      ..setNavigationDelegate(
        NavigationDelegate(
          onProgress: (int progress) {
            debugPrint('WebView is loading (progress : $progress%)');
          },
          onPageStarted: (String url) {
            debugPrint('Page started loading: $url');
          },
          onPageFinished: (String url) {
            debugPrint('Page finished loading: $url');
          },
          onWebResourceError: (WebResourceError error) {
            debugPrint('''
Page resource error:
  code: ${error.errorCode}
  description: ${error.description}
  errorType: ${error.errorType}
  isForMainFrame: ${error.isForMainFrame}
          ''');
          },
          onNavigationRequest: (NavigationRequest request) {
            if (request.url.startsWith('https://www.youtube.com/')) {
              debugPrint('blocking navigation to ${request.url}');
              return NavigationDecision.prevent;
            }
            debugPrint('allowing navigation to ${request.url}');
            return NavigationDecision.navigate;
          },
          onHttpError: (HttpResponseError error) {
            debugPrint('Error occurred on page: ${error.response?.statusCode}');
          },
          onUrlChange: (UrlChange change) {
            debugPrint('url change to ${change.url}');
          },
          onHttpAuthRequest: (HttpAuthRequest request) {
            openDialog(request);
          },
        ),
      )
      ..addJavaScriptChannel(
        'Toaster',
        onMessageReceived: (JavaScriptMessage message) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(content: Text(message.message)),
          );
        },
      )
      ..loadRequest(Uri.parse('https://flutter.dev'));

    // #docregion platform_features
    if (controller.platform is AndroidWebViewController) {
      AndroidWebViewController.enableDebugging(true);
      (controller.platform as AndroidWebViewController)
          .setMediaPlaybackRequiresUserGesture(false);
    }
    // #enddocregion platform_features

    _controller = controller;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.green,
      appBar: AppBar(
        title: const Text('Flutter WebView example'),
        // This drop down menu demonstrates that Flutter widgets can be shown over the web view.
        actions: <Widget>[
          NavigationControls(webViewController: _controller),
          SampleMenu(webViewController: _controller),
        ],
      ),
      body: WebViewWidget(controller: _controller),
      floatingActionButton: favoriteButton(),
    );
  }

  Widget favoriteButton() {
    return FloatingActionButton(
      onPressed: () async {
        final String? url = await _controller.currentUrl();
        if (mounted) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(content: Text('Favorited $url')),
          );
        }
      },
      child: const Icon(Icons.favorite),
    );
  }

  Future<void> openDialog(HttpAuthRequest httpRequest) async {
    final TextEditingController usernameTextController =
        TextEditingController();
    final TextEditingController passwordTextController =
        TextEditingController();

    return showDialog(
      context: context,
      barrierDismissible: false,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text('${httpRequest.host}: ${httpRequest.realm ?? '-'}'),
          content: SingleChildScrollView(
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: <Widget>[
                TextField(
                  decoration: const InputDecoration(labelText: 'Username'),
                  autofocus: true,
                  controller: usernameTextController,
                ),
                TextField(
                  decoration: const InputDecoration(labelText: 'Password'),
                  controller: passwordTextController,
                ),
              ],
            ),
          ),
          actions: <Widget>[
            // Explicitly cancel the request on iOS as the OS does not emit new
            // requests when a previous request is pending.
            TextButton(
              onPressed: () {
                httpRequest.onCancel();
                Navigator.of(context).pop();
              },
              child: const Text('Cancel'),
            ),
            TextButton(
              onPressed: () {
                httpRequest.onProceed(
                  WebViewCredential(
                    user: usernameTextController.text,
                    password: passwordTextController.text,
                  ),
                );
                Navigator.of(context).pop();
              },
              child: const Text('Authenticate'),
            ),
          ],
        );
      },
    );
  }
}

enum MenuOptions {
  showUserAgent,
  listCookies,
  clearCookies,
  addToCache,
  listCache,
  clearCache,
  navigationDelegate,
  doPostRequest,
  loadLocalFile,
  loadFlutterAsset,
  loadHtmlString,
  transparentBackground,
  setCookie,
  logExample,
  basicAuthentication,
}

class SampleMenu extends StatelessWidget {
  SampleMenu({
    super.key,
    required this.webViewController,
  });

  final WebViewController webViewController;
  late final WebViewCookieManager cookieManager = WebViewCookieManager();

  @override
  Widget build(BuildContext context) {
    return PopupMenuButton<MenuOptions>(
      key: const ValueKey<String>('ShowPopupMenu'),
      onSelected: (MenuOptions value) {
        switch (value) {
          case MenuOptions.showUserAgent:
            _onShowUserAgent();
          case MenuOptions.listCookies:
            _onListCookies(context);
          case MenuOptions.clearCookies:
            _onClearCookies(context);
          case MenuOptions.addToCache:
            _onAddToCache(context);
          case MenuOptions.listCache:
            _onListCache();
          case MenuOptions.clearCache:
            _onClearCache(context);
          case MenuOptions.navigationDelegate:
            _onNavigationDelegateExample();
          case MenuOptions.doPostRequest:
            _onDoPostRequest();
          case MenuOptions.loadLocalFile:
            _onLoadLocalFileExample();
          case MenuOptions.loadFlutterAsset:
            _onLoadFlutterAssetExample();
          case MenuOptions.loadHtmlString:
            _onLoadHtmlStringExample();
          case MenuOptions.transparentBackground:
            _onTransparentBackground();
          case MenuOptions.setCookie:
            _onSetCookie();
          case MenuOptions.logExample:
            _onLogExample();
          case MenuOptions.basicAuthentication:
            _promptForUrl(context);
        }
      },
      itemBuilder: (BuildContext context) => <PopupMenuItem<MenuOptions>>[
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.showUserAgent,
          child: Text('Show user agent'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.listCookies,
          child: Text('List cookies'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.clearCookies,
          child: Text('Clear cookies'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.addToCache,
          child: Text('Add to cache'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.listCache,
          child: Text('List cache'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.clearCache,
          child: Text('Clear cache'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.navigationDelegate,
          child: Text('Navigation Delegate example'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.doPostRequest,
          child: Text('Post Request'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.loadHtmlString,
          child: Text('Load HTML string'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.loadLocalFile,
          child: Text('Load local file'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.loadFlutterAsset,
          child: Text('Load Flutter Asset'),
        ),
        const PopupMenuItem<MenuOptions>(
          key: ValueKey<String>('ShowTransparentBackgroundExample'),
          value: MenuOptions.transparentBackground,
          child: Text('Transparent background example'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.setCookie,
          child: Text('Set cookie'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.logExample,
          child: Text('Log example'),
        ),
        const PopupMenuItem<MenuOptions>(
          value: MenuOptions.basicAuthentication,
          child: Text('Basic Authentication Example'),
        ),
      ],
    );
  }

  Future<void> _onShowUserAgent() {
    // Send a message with the user agent string to the Toaster JavaScript channel we registered
    // with the WebView.
    return webViewController.runJavaScript(
      'Toaster.postMessage("User Agent: " + navigator.userAgent);',
    );
  }

  Future<void> _onListCookies(BuildContext context) async {
    final String cookies = await webViewController
        .runJavaScriptReturningResult('document.cookie') as String;
    if (context.mounted) {
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(
        content: Column(
          mainAxisAlignment: MainAxisAlignment.end,
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            const Text('Cookies:'),
            _getCookieList(cookies),
          ],
        ),
      ));
    }
  }

  Future<void> _onAddToCache(BuildContext context) async {
    await webViewController.runJavaScript(
      'caches.open("test_caches_entry"); localStorage["test_localStorage"] = "dummy_entry";',
    );
    if (context.mounted) {
      ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
        content: Text('Added a test entry to cache.'),
      ));
    }
  }

  Future<void> _onListCache() {
    return webViewController.runJavaScript('caches.keys()'
        // ignore: missing_whitespace_between_adjacent_strings
        '.then((cacheKeys) => JSON.stringify({"cacheKeys" : cacheKeys, "localStorage" : localStorage}))'
        '.then((caches) => Toaster.postMessage(caches))');
  }

  Future<void> _onClearCache(BuildContext context) async {
    await webViewController.clearCache();
    await webViewController.clearLocalStorage();
    if (context.mounted) {
      ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
        content: Text('Cache cleared.'),
      ));
    }
  }

  Future<void> _onClearCookies(BuildContext context) async {
    final bool hadCookies = await cookieManager.clearCookies();
    String message = 'There were cookies. Now, they are gone!';
    if (!hadCookies) {
      message = 'There are no cookies.';
    }
    if (context.mounted) {
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(
        content: Text(message),
      ));
    }
  }

  Future<void> _onNavigationDelegateExample() {
    final String contentBase64 = base64Encode(
      const Utf8Encoder().convert(kNavigationExamplePage),
    );
    return webViewController.loadRequest(
      Uri.parse('data:text/html;base64,$contentBase64'),
    );
  }

  Future<void> _onSetCookie() async {
    await cookieManager.setCookie(
      const WebViewCookie(
        name: 'foo',
        value: 'bar',
        domain: 'httpbin.org',
        path: '/anything',
      ),
    );
    await webViewController.loadRequest(Uri.parse(
      'https://httpbin.org/anything',
    ));
  }

  Future<void> _onDoPostRequest() {
    return webViewController.loadRequest(
      Uri.parse('https://httpbin.org/post'),
      method: LoadRequestMethod.post,
      headers: <String, String>{'foo': 'bar', 'Content-Type': 'text/plain'},
      body: Uint8List.fromList('Test Body'.codeUnits),
    );
  }

  Future<void> _onLoadLocalFileExample() async {
    final String pathToIndex = await _prepareLocalFile();
    await webViewController.loadFile(pathToIndex);
  }

  Future<void> _onLoadFlutterAssetExample() {
    return webViewController.loadFlutterAsset('assets/www/index.html');
  }

  Future<void> _onLoadHtmlStringExample() {
    return webViewController.loadHtmlString(kLocalExamplePage);
  }

  Future<void> _onTransparentBackground() {
    return webViewController.loadHtmlString(kTransparentBackgroundPage);
  }

  Widget _getCookieList(String cookies) {
    if (cookies == '""') {
      return Container();
    }
    final List<String> cookieList = cookies.split(';');
    final Iterable<Text> cookieWidgets =
        cookieList.map((String cookie) => Text(cookie));
    return Column(
      mainAxisAlignment: MainAxisAlignment.end,
      mainAxisSize: MainAxisSize.min,
      children: cookieWidgets.toList(),
    );
  }

  static Future<String> _prepareLocalFile() async {
    final String tmpDir = (await getTemporaryDirectory()).path;
    final File indexFile = File(
        <String>{tmpDir, 'www', 'index.html'}.join(Platform.pathSeparator));

    await indexFile.create(recursive: true);
    await indexFile.writeAsString(kLocalExamplePage);

    return indexFile.path;
  }

  Future<void> _onLogExample() {
    webViewController
        .setOnConsoleMessage((JavaScriptConsoleMessage consoleMessage) {
      debugPrint(
          '== JS == ${consoleMessage.level.name}: ${consoleMessage.message}');
    });

    return webViewController.loadHtmlString(kLogExamplePage);
  }

  Future<void> _promptForUrl(BuildContext context) {
    final TextEditingController urlTextController = TextEditingController();

    return showDialog<String>(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text('Input URL to visit'),
          content: TextField(
            decoration: const InputDecoration(labelText: 'URL'),
            autofocus: true,
            controller: urlTextController,
          ),
          actions: <Widget>[
            TextButton(
              onPressed: () {
                if (urlTextController.text.isNotEmpty) {
                  final Uri? uri = Uri.tryParse(urlTextController.text);
                  if (uri != null && uri.scheme.isNotEmpty) {
                    webViewController.loadRequest(uri);
                    Navigator.pop(context);
                  }
                }
              },
              child: const Text('Visit'),
            ),
          ],
        );
      },
    );
  }
}

class NavigationControls extends StatelessWidget {
  const NavigationControls({super.key, required this.webViewController});

  final WebViewController webViewController;

  @override
  Widget build(BuildContext context) {
    return Row(
      children: <Widget>[
        IconButton(
          icon: const Icon(Icons.arrow_back_ios),
          onPressed: () async {
            if (await webViewController.canGoBack()) {
              await webViewController.goBack();
            } else {
              if (context.mounted) {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(content: Text('No back history item')),
                );
              }
            }
          },
        ),
        IconButton(
          icon: const Icon(Icons.arrow_forward_ios),
          onPressed: () async {
            if (await webViewController.canGoForward()) {
              await webViewController.goForward();
            } else {
              if (context.mounted) {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(content: Text('No forward history item')),
                );
              }
            }
          },
        ),
        IconButton(
          icon: const Icon(Icons.replay),
          onPressed: () => webViewController.reload(),
        ),
      ],
    );
  }
}

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// ignore_for_file: public_member_api_docs

import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

void main() => runApp(const MaterialApp(home: WebViewExample()));

class WebViewExample extends StatefulWidget {
  const WebViewExample({super.key});

  @override
  State<WebViewExample> createState() => _WebViewExampleState();
}

class _WebViewExampleState extends State<WebViewExample> {
  late final WebViewController controller;

  @override
  void initState() {
    super.initState();

    // #docregion webview_controller
    controller = WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..setBackgroundColor(const Color(0x00000000))
      ..setNavigationDelegate(
        NavigationDelegate(
          onProgress: (int progress) {
            // Update loading bar.
          },
          onPageStarted: (String url) {},
          onPageFinished: (String url) {},
          onHttpError: (HttpResponseError error) {},
          onWebResourceError: (WebResourceError error) {},
          onNavigationRequest: (NavigationRequest request) {
            if (request.url.startsWith('https://www.youtube.com/')) {
              return NavigationDecision.prevent;
            }
            return NavigationDecision.navigate;
          },
        ),
      )
      ..loadRequest(Uri.parse('https://flutter.dev'));
    // #enddocregion webview_controller
  }

  // #docregion webview_widget
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Flutter Simple Example')),
      body: WebViewWidget(controller: controller),
    );
  }
  // #enddocregion webview_widget
}

```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

https://github.com/user-attachments/assets/7855eb85-a93d-461e-b4fd-81add68f5252

</details>


### Logs

<details open><summary>Logs</summary>

```console
No specific logs
```

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[!] Flutter (Channel [user-branch], 3.19.6, on macOS 14.5 23F79 darwin-arm64, locale en-IN)
    ! Flutter version 3.19.6 on channel [user-branch] at /Users/piyushanand/development/FlutterSDK/flutter
      Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
      If that doesn't fix the issue, reinstall Flutter by following instructions at https://flutter.dev/docs/get-started/install.
    ! Upstream repository unknown source is not a standard remote.
      Set environment variable "FLUTTER_GIT_URL" to unknown source to dismiss this error.
    • Framework revision 54e66469a9 (3 months ago), 2024-04-17 13:08:03 -0700
    • Engine revision c4cd48e186
    • Dart version 3.3.4
    • DevTools version 2.31.1
    • If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/piyushanand/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • ANDROID_HOME = /Users/piyushanand/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.4)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 15F31d
    • CocoaPods version 1.14.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2023.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)

[✓] VS Code (version 1.91.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.92.0

[✓] Connected device (3 available)
    • iPhone 15 Pro Max (mobile) • E9C45BE5-1DF1-43F6-83F7-EA52F935226F • ios            • com.apple.CoreSimulator.SimRuntime.iOS-17-5 (simulator)
    • macOS (desktop)            • macos                                • darwin-arm64   • macOS 14.5 23F79 darwin-arm64
    • Chrome (web)               • chrome                               • web-javascript • Google Chrome 126.0.6478.127
    ! Error: Browsing on the local area network for Piyush’s iPhone. Ensure the device is unlocked and attached with a cable or associated with the same local area
      network as this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)
    ! Error: Browsing on the local area network for iPhone . Ensure the device is unlocked and attached with a cable or associated with the same local area network as
      this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

```

</details>