ListWheelScrollView throws "Null check operator used on a null value" while loading images #125997

Activity

1. Sarraj-Sahar commented on May 3, 2023

   

   Sarraj-Sahar

   on May 3, 2023

   More actions

   Are you sure the issue isn't related to the network image link you're providing ? I changed the URL and it works for me.

   

   Code sample

   void main(List<String> args) {
     runApp(
       MaterialApp(
         home: Scaffold(
           body: ListWheelScrollView.useDelegate(
             itemExtent: 400,
             childDelegate: ListWheelChildLoopingListDelegate(
               children: List.generate(
                20,
                //changed image url
                   (i) => Image.network('https://picsum.photos/200')),
             ),
           ),
         ),
       ),
     );
   }
2. Z6P0 commented on May 3, 2023

   

   Z6P0

   on May 3, 2023

   Author

   More actions

   I tried with your image URL and many others and it's the same bug.
   I also tried with different Android emulator versions.
3. darshankawar

   added

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   on May 4, 2023
4. darshankawar commented on May 4, 2023

   

   darshankawar

   on May 4, 2023

   Member

   More actions

   Thanks for the report. Using the code sample provided and with different urls, I am able to replicate the reported error using latest master and stable versions.
   I think it has to do with the type of childDelegate you are passing, in this case, is ListWheelChildLoopingListDelegate.

   I tried with another childDelegate as below with which too it throws the same error.

   return Scaffold(
         body: ListWheelScrollView.useDelegate(
           itemExtent: 400,
           physics: FixedExtentScrollPhysics(),
           childDelegate: ListWheelChildBuilderDelegate(
             builder: (context, index) => Image.network(
               'https://via.placeholder.com/400',
               height: 160,
               width: 160,
             ),
           ),
         ),
       );
   

   stable, master flutter doctor -v

   [!] Flutter (Channel stable, 3.7.12, on macOS 12.2.1 21D62 darwin-x64, locale
       en-GB)
       • Flutter version 3.7.12 on channel stable at
         /Users/dhs/documents/fluttersdk/flutter
       ! Warning: `flutter` on your path resolves to
         /Users/dhs/Documents/Fluttersdk/flutter/bin/flutter, which is not inside
         your current Flutter SDK checkout at
         /Users/dhs/documents/fluttersdk/flutter. Consider adding
         /Users/dhs/documents/fluttersdk/flutter/bin to the front of your path.
       ! Warning: `dart` on your path resolves to
         /Users/dhs/Documents/Fluttersdk/flutter/bin/dart, which is not inside your
         current Flutter SDK checkout at /Users/dhs/documents/fluttersdk/flutter.
         Consider adding /Users/dhs/documents/fluttersdk/flutter/bin to the front
         of your path.
       • Upstream repository https://github.com/flutter/flutter.git
       • Framework revision 4d9e56e694 (3 days ago), 2023-04-17 21:47:46 -0400
       • Engine revision 1a65d409c7
       • Dart version 2.19.6
       • DevTools version 2.20.1
       • If those were intentional, you can disregard the above warnings; however
         it is recommended to use "git" directly to perform update checks and
         upgrades.
   
   [!] Xcode - develop for iOS and macOS (Xcode 12.3)
       • Xcode at /Applications/Xcode.app/Contents/Developer
       ! Flutter recommends a minimum Xcode version of 13.
         Download the latest version or update via the Mac App Store.
       • CocoaPods version 1.11.2
   
   [✓] Chrome - develop for the web
       • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
   
   [✓] VS Code (version 1.62.0)
       • VS Code at /Applications/Visual Studio Code.app/Contents
       • Flutter extension version 3.21.0
   
   [✓] Connected device (5 available)
       • SM G975F (mobile)       • RZ8M802WY0X • android-arm64   • Android 11 (API 30)
       • Darshan's iphone (mobile)  • 21150b119064aecc249dfcfe05e259197461ce23 •
         ios            • iOS 14.4.1 18D61
       • iPhone 12 Pro Max (mobile) • A5473606-0213-4FD8-BA16-553433949729     •
         ios            • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator)
       • macOS (desktop)            • macos                                    •
         darwin-x64     • Mac OS X 10.15.4 19E2269 darwin-x64
       • Chrome (web)               • chrome                                   •
         web-javascript • Google Chrome 98.0.4758.80
   
   [✓] HTTP Host Availability
       • All required HTTP hosts are available
   
   ! Doctor found issues in 1 category.
   
   [!] Flutter (Channel master, 3.11.0-1.0.pre.44, on macOS 12.2.1 21D62
       darwin-x64, locale en-GB)
       • Flutter version 3.11.0-1.0.pre.44 on channel master at
         /Users/dhs/documents/fluttersdk/flutter
       ! Warning: `flutter` on your path resolves to
         /Users/dhs/Documents/Fluttersdk/flutter/bin/flutter, which is not inside
         your current Flutter SDK checkout at
         /Users/dhs/documents/fluttersdk/flutter. Consider adding
         /Users/dhs/documents/fluttersdk/flutter/bin to the front of your path.
       ! Warning: `dart` on your path resolves to
         /Users/dhs/Documents/Fluttersdk/flutter/bin/dart, which is not inside your
         current Flutter SDK checkout at /Users/dhs/documents/fluttersdk/flutter.
         Consider adding /Users/dhs/documents/fluttersdk/flutter/bin to the front
         of your path.
       • Upstream repository https://github.com/flutter/flutter.git
       • Framework revision ebf3ea1755 (2 hours ago), 2023-05-03 23:25:08 -0400
       • Engine revision da45a21708
       • Dart version 3.1.0 (build 3.1.0-72.0.dev)
       • DevTools version 2.23.1
       • 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 30.0.3)
       • Android SDK at /Users/dhs/Library/Android/sdk
       ✗ cmdline-tools component is missing
         Run `path/to/sdkmanager --install "cmdline-tools;latest"`
         See https://developer.android.com/studio/command-line for more details.
       ✗ Android license status unknown.
         Run `flutter doctor --android-licenses` to accept the SDK licenses.
         See https://flutter.dev/docs/get-started/install/macos#android-setup for
         more details.
   
   [✓] Xcode - develop for iOS and macOS (Xcode 13.2.1)
       • Xcode at /Applications/Xcode.app/Contents/Developer
       • Build 13C100
       • CocoaPods version 1.11.2
   
   [✓] Chrome - develop for the web
       • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
   
   [✓] IntelliJ IDEA Ultimate Edition (version 2021.3.2)
       • IntelliJ at /Applications/IntelliJ IDEA.app
       • Flutter plugin version 65.1.4
       • Dart plugin version 213.7228
   
   [✓] VS Code (version 1.62.0)
       • VS Code at /Applications/Visual Studio Code.app/Contents
       • Flutter extension version 3.29.0
   
   [✓] Connected device (3 available)
       • Darshan's iphone (mobile) • 21150b119064aecc249dfcfe05e259197461ce23 • ios
         • iOS 15.3.1 19D52
       • macOS (desktop)           • macos                                    •
         darwin-x64     • macOS 12.2.1 21D62 darwin-x64
       • Chrome (web)              • chrome                                   •
         web-javascript • Google Chrome 109.0.5414.119
   
   [✓] Network resources
       • All expected network resources are available.
   
   ! Doctor found issues in 1 category.
         
   [!] Xcode - develop for iOS and macOS (Xcode 12.3)
       • Xcode at /Applications/Xcode.app/Contents/Developer
       ! Flutter recommends a minimum Xcode version of 13.
         Download the latest version or update via the Mac App Store.
       • CocoaPods version 1.11.2
   
   [✓] Chrome - develop for the web
       • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
   
   [✓] VS Code (version 1.62.0)
       • VS Code at /Applications/Visual Studio Code.app/Contents
       • Flutter extension version 3.21.0
   
   [✓] Connected device (5 available)
       • SM G975F (mobile)       • RZ8M802WY0X • android-arm64   • Android 11 (API 30)
       • Darshan's iphone (mobile)  • 21150b119064aecc249dfcfe05e259197461ce23 •
         ios            • iOS 14.4.1 18D61
       • iPhone 12 Pro Max (mobile) • A5473606-0213-4FD8-BA16-553433949729     •
         ios            • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator)
       • macOS (desktop)            • macos                                    •
         darwin-x64     • Mac OS X 10.15.4 19E2269 darwin-x64
       • Chrome (web)               • chrome                                   •
         web-javascript • Google Chrome 98.0.4758.80
   
   [✓] HTTP Host Availability
       • All required HTTP hosts are available
   
   ! Doctor found issues in 1 category.
   
   
   
   
5. darshankawar

   added

   frameworkflutter/packages/flutter repository. See also f: labels.flutter/packages/flutter repository. See also f: labels.

   p: material_uimaterial_ui package in flutter/packagesmaterial_ui package in flutter/packages

   has reproducible stepsThe issue has been confirmed reproducible and is ready to work onThe issue has been confirmed reproducible and is ready to work on

   found in release: 3.7Found to occur in 3.7Found to occur in 3.7

   found in release: 3.11Found to occur in 3.11Found to occur in 3.11

   c: crashStack traces logged to the consoleStack traces logged to the console

   a: error messageError messages from the Flutter frameworkError messages from the Flutter framework

   a: imagesLoading, displaying, rendering imagesLoading, displaying, rendering images

   and removed

   in triagePresently being triaged by the triage teamPresently being triaged by the triage team

   on May 4, 2023
6. TahaTesser

   removed

   p: material_uimaterial_ui package in flutter/packagesmaterial_ui package in flutter/packages

   on May 4, 2023
7. TahaTesser commented on May 4, 2023

   

   TahaTesser

   on May 4, 2023

   Contributor

   More actions

   ListWheelScrollView is not a material widget.
   https://api.flutter.dev/flutter/widgets/ListWheelScrollView-class.html

   👍React with 👍1Reacted by darshankawar
8. darshankawar

   added

   f: scrollingViewports, list views, slivers, etc.Viewports, list views, slivers, etc.

   on May 5, 2023
9. goderbauer

   added

   P2Important issues not at the top of the work listImportant issues not at the top of the work list

   on May 10, 2023
10. flutter-triage-bot

    added

    team-frameworkOwned by Framework teamOwned by Framework team

    triaged-frameworkTriaged by Framework teamTriaged by Framework team

    on Jul 8, 2023
11. hgandhi67 commented on Sep 7, 2023

    

    hgandhi67

    on Sep 7, 2023

    More actions

    Able to reproduce in 3.13.3 version as well.
12. bpjhe commented on Jan 29, 2025

    

    bpjhe

    on Jan 29, 2025

    More actions

    Just wanted to chime in and say I stumbled upon the same problem (v3.27.1). Been trying to find a workaround but no luck. I managed to get the initial selected item to load an image by using a custom image provider, but the other ones on the screen will not load until they have been off-screen.
13. auto-submit

    closed this as completedin #194859on Nov 6, 2026
14. victorsanni

    added a commit that references this issue on Nov 6, 2026

    Fix ListWheelScrollView null check error when it reads itemIndex befo…

    ...

    This issue will close once commit 45c517a is merged into the 'master' branch.

    45c517a