[Accessibility] Talkback doesn't announce anything about `Slider` when focused

[adil-s]

the material slider has issue on android with talkback. when a user focuses on using talk back swipes, the talk back doesn't announce the value of slider. the talkback doesn't recognise the slider and I only hear the sound feetback that there is something here, but no spoken feetback.
when I use explore by touch to find the slider, talkback behave as expected.

Steps to Reproduce

1. clone the slider interactive app from the link: https://api.flutter.dev/flutter/material/Slider-class.html
2. enable the talkback on actual android device
3. run the app and try exploring the app using talk back gestures (swipe left and right)
4. when talkback focuses on slider, it doesn't announce anything.
5. swipe right and then left in continuous motion to increase the slider value.
6. the slider value increases and talkback gives the proper spoken feetback.

Expected results:

I expect talkback to announce the slider whenever it gains the focus on the slider.
Actual results:
currently, talkbacck doesn't announce anything when slider is focused.
flutter run -v output:

Microsoft Windows [Version 10.0.19042.868]
(c) 2020 Microsoft Corporation. All rights reserved.

flutter doctor -v

[√] Flutter (Channel stable, 2.0.3, on Microsoft Windows [Version 10.0.19042.868], locale en-US)
    • Flutter version 2.0.3 at C:\tools\flutter
    • Framework revision 4d7946a68d (13 days ago), 2021-03-18 17:24:33 -0700
    • Engine revision 3459eb2436
    • Dart version 2.12.2

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at C:\Android\android-sdk
    • Platform android-30, build-tools 30.0.2
    • ANDROID_HOME = C:\Android\android-sdk
    • Java binary at: C:\Program Files\Java\jdk1.8.0_211\bin\java
    • Java version Java(TM) SE Runtime Environment (build 1.8.0_211-b12)
    • All Android licenses accepted.

[X] Chrome - develop for the web (Cannot find Chrome executable at .\Google\Chrome\Application\chrome.exe)
    ! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).

[√] VS Code, 64-bit edition (version 1.54.3)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 3.20.0

[√] Connected device (2 available)
    • Mi A2 (mobile) • 4add0e2 • android-arm64  • Android 11 (API 30)
    • Edge (web)     • edge    • web-javascript • Microsoft Edge 89.0.774.63

! Doctor found issues in 2 categories.

[darshankawar]

Verified this on latest stable and although the slider value (percentage, example 60%) and its changes are read properly on iOS, on Android, it doesn't read.

flutter doctor -v

[✓] Flutter (Channel stable, 2.0.3, on Mac OS X 10.15.4 19E2269 darwin-x64,
    locale en-GB)
    • Flutter version 2.0.3 at /Users/dhs/documents/Fluttersdk/flutter
    • Framework revision 4d7946a68d (13 days ago), 2021-03-18 17:24:33 -0700
    • Engine revision 3459eb2436
    • Dart version 2.12.2

[!] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.3, Build version 12C33
    ! CocoaPods 1.9.3 out of date (1.10.0 is recommended).
        CocoaPods is used to retrieve the iOS and macOS platform side's plugin
        code that responds to your plugin usage on the Dart side.
        Without CocoaPods, plugins will not work on iOS or macOS.
        For more info, see https://flutter.dev/platform-plugins
      To upgrade see
      https://guides.cocoapods.org/using/getting-started.html#installation for
      instructions.

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] VS Code (version 1.54.3)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.20.0

[✓] Connected device (3 available)
    • Darshan's iphone (mobile) • 21150b119064aecc249dfcfe05e259197461ce23 • ios
      • iOS 14.4.1
    • macOS (desktop)           • macos                                    •
      darwin-x64     • Mac OS X 10.15.4 19E2269 darwin-x64
    • Chrome (web)              • chrome                                   •
      web-javascript • Google Chrome 89.0.4389.114

! Doctor found issues in 1 category.

[TahaTesser]

Reproduced the issue using the following minimal code sample

minimal code sample

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter accessibility issues demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter accessibility issues demo page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _currentIndex = 0;
  bool _extendBody = false;
  List<Widget> bodyList = [SliderPage(), ListTilePage(), NestedListViewPage()];

  void onTap(int index) {
    setState(() {
      _currentIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Scaffold(
        appBar: AppBar(
          title: Text("Demo"),
          actions: [
            Tooltip(
              message: 'Til baka',
              child: FlatButton(
                child: Text(
                    _extendBody ? "Disable extend body" : "Enable extend body"),
                onPressed: () {
                  setState(() {
                    _extendBody = !_extendBody;
                  });
                },
              ),
            )
          ],
        ),
        body: bodyList[_currentIndex],
        extendBody: _extendBody,
        bottomNavigationBar: BottomNavigationBar(
          elevation: 0,
          type: BottomNavigationBarType.fixed,
          showUnselectedLabels: true,
          onTap: onTap,
          currentIndex: _currentIndex,
          items: [
            // Screen reader speaks the label text two times for each item
            // "Slider page example, Slider page example, tab 1 of 3, double tap to activate.
            BottomNavigationBarItem(
                label: 'Slider page example', icon: Icon(Icons.tv, size: 20.0)),
            BottomNavigationBarItem(
                label: 'Tiles in ListView',
                icon: Icon(Icons.radio, size: 20.0)),
            BottomNavigationBarItem(
                label: 'Nested ListView example',
                icon: Icon(Icons.live_tv, size: 20.0)),
          ],
        ),
      ),
    );
  }
}

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

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

class _SliderPageState extends State<SliderPage> {
  double sliderValue = 0.0;
  double onChangeEndValue = 0.0;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text('sliderValue: $sliderValue'),
        Text('onChangeEnd: $onChangeEndValue'),
        Slider(
            value: sliderValue,
            min: 0.0,
            onChangeStart: (e) {
              print("onChangeStart: $e");
            },
            onChanged: (e) {
              print("onChanged: $e");
              setState(() {
                sliderValue = e;
              });
            },
            onChangeEnd: (e) {
              print("onChangeEnd: $e");
              setState(() {
                sliderValue = e;
                onChangeEndValue = e;
              });
            }),
      ],
    );
  }
}

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

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

class _ListTilePageState extends State<ListTilePage> {
  double sliderValue = 0.0;
  double onChangeEndValue = 0.0;

  @override
  Widget build(BuildContext context) {
    return ListView(
        children: List<Widget>.generate(
            200, (index) => ListTile(title: Text('Item number $index'))));
  }
}

class NestedListViewPage extends StatefulWidget {
  @override
  _NestedListViewPageState createState() => _NestedListViewPageState();
}

class _NestedListViewPageState extends State<NestedListViewPage> {
  @override
  Widget build(BuildContext context) {
    return ListView(
      scrollDirection: Axis.vertical,
      children: List<Widget>.generate(
        50,
        (index1) => Container(
          height: 100,
          child: ListView(
            scrollDirection: Axis.horizontal,
            children: List<Widget>.generate(
                10,
                (index2) => GestureDetector(
                      onTap: () => null,
                      child: Center(child: Text('Row $index1, Line $index2')),
                    )),
          ),
        ),
      ),
    );
  }
}

Reproduced on the following channels

stable	master
❌	❌

Check flutter doctor -v outputs for each channel below

flutter doctor -v

[✓] Flutter (Channel stable, 2.2.0, on Microsoft Windows [Version 10.0.19042.964], locale en-US)
    • Flutter version 2.2.0 at C:\Users\Taha\Code\flutter_stable
    • Framework revision b22742018b (4 days ago), 2021-05-14 19:12:57 -0700
    • Engine revision a9d88a4d18
    • Dart version 2.13.0

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\Users\Taha\Code\SDK
    • Platform android-30, build-tools 30.0.3
    • Java binary at: C:\Users\Taha\Code\android-studio\jre\bin\java.exe
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6842174)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[✓] Visual Studio - develop for Windows (Visual Studio Community 2019 16.9.5)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community
    • Visual Studio Community 2019 version 16.9.31229.75
    • Windows 10 SDK version 10.0.19041.0

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/windows#android-setup for detailed instructions).

[✓] VS Code (version 1.56.2)
    • VS Code at C:\Users\Taha\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.22.0

[✓] Connected device (4 available)
    • Redmi K20 Pro (mobile) • def0ad20 • android-arm64  • Android 10 (API 29)
    • Windows (desktop)      • windows  • windows-x64    • Microsoft Windows [Version 10.0.19042.964]
    • Chrome (web)           • chrome   • web-javascript • Google Chrome 90.0.4430.212
    • Edge (web)             • edge     • web-javascript • Microsoft Edge 89.0.774.63

! Doctor found issues in 1 category.

[✓] Flutter (Channel master, 2.3.0-13.0.pre.33, on Microsoft Windows [Version 10.0.19042.964], locale en-US)
    • Flutter version 2.3.0-13.0.pre.33 at C:\Users\Taha\Code\flutter_master
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 84734ecc54 (in the future), 2021-05-18 23:09:03 -0700
    • Engine revision 2398dea918
    • Dart version 2.14.0 (build 2.14.0-119.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\Users\Taha\Code\SDK
    • Platform android-30, build-tools 30.0.3
    • Java binary at: C:\Users\Taha\Code\android-studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6842174)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[✓] Visual Studio - develop for Windows (Visual Studio Community 2019 16.9.5)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community
    • Visual Studio Community 2019 version 16.9.31229.75
    • Windows 10 SDK version 10.0.19041.0

[✓] Android Studio (version 4.2.0)
    • Android Studio at C:\Users\Taha\Code\android-studio
    • 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 11.0.8+10-b944.6842174)

[✓] VS Code (version 1.56.2)
    • VS Code at C:\Users\Taha\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.22.0

[✓] Connected device (5 available)
    • Redmi K20 Pro (mobile)  • def0ad20 • android-arm64   • Android 10 (API 29)
    • Windows (desktop)       • windows  • windows-x64     • Microsoft Windows [Version 10.0.19042.964]
    • Windows (UWP) (desktop) • winuwp   • windows-uwp-x64 •
    • Chrome (web)            • chrome   • web-javascript  • Google Chrome 90.0.4430.212
    • Edge (web)              • edge     • web-javascript  • Microsoft Edge 89.0.774.63

• No issues found!

✅: No Issue ❌: Issue reproduced

[KiruthikaAdhi]

Kindly fix this issue. This is particularly happening with recent talkback update version 9.1. Is there any workaround that is available for now? I am facing this issue in my production app and users are not able to use certain features due to this issue.