list_wheel_scroll_view.dart throws Null check operator used on a null value error while loading images #60578

Activity

1. darshankawar commented on Jun 30, 2020

   

   darshankawar

   on Jun 30, 2020

   Member

   More actions

   Hi @Faiyyaz,
   Can you please provide a minimal complete reproducible code sample.
   Thank you.
2. darshankawar

   added

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

   waiting for responseThe Flutter team cannot make further progress on this issue until the original reporter respondsThe Flutter team cannot make further progress on this issue until the original reporter responds

   on Jun 30, 2020
3. Faiyyaz commented on Jun 30, 2020

   

   Faiyyaz

   on Jun 30, 2020

   Last edited by Faiyyaz

   Author

   More actions

   This is the class of a pub named country picker https://pub.dev/packages/country_pickers and this class internally uses the list_wheel_scroll_view.dart which returns the error

   import 'package:country_pickers/countries.dart';
   import 'package:country_pickers/country.dart';
   import 'package:country_pickers/utils/typedefs.dart';
   import 'package:country_pickers/utils/utils.dart';
   import 'package:flutter/cupertino.dart';
   import 'dart:core';
   
   const double defaultPickerSheetHeight = 216.0;
   const double defaultPickerItemHeight = 32.0;
   
   /// Color of picker background
   const Color _kDefaultBackground = Color(0xFFD2D4DB);
   
   // Eyeballed values comparing with a native picker.
   // Values closer to PI produces denser flatter lists.
   const double _kDefaultDiameterRatio = 1.35;
   
   ///Provides a customizable [CupertinoPicker] which displays all countries
   /// in cupertino style
   class CountryPickerCupertino extends StatefulWidget {
     /// Callback that is called with selected Country
     final ValueChanged<Country> onValuePicked;
   
     /// Filters the available country list
     final ItemFilter itemFilter;
   
     /// [Comparator] to be used in sort of country list
     final Comparator<Country> sortComparator;
   
     /// List of countries that are placed on top
     final List<Country> priorityList;
   
     ///Callback that is called with selected item of type Country which returns a
     ///Widget to build list view item inside dialog
     final ItemBuilder itemBuilder;
   
     ///The [itemExtent] of [CupertinoPicker]
     /// The uniform height of all children.
     ///
     /// All children will be given the [BoxConstraints] to match this exact
     /// height. Must not be null and must be positive.
     final double pickerItemHeight;
   
     ///The height of the picker
     final double pickerSheetHeight;
   
     ///The TextStyle that is applied to Text widgets inside item
     final TextStyle textStyle;
   
     /// Relative ratio between this picker's height and the simulated cylinder's diameter.
     ///
     /// Smaller values creates more pronounced curvatures in the scrollable wheel.
     ///
     /// For more details, see [ListWheelScrollView.diameterRatio].
     ///
     /// Must not be null and defaults to `1.1` to visually mimic iOS.
     final double diameterRatio;
   
     /// Background color behind the children.
     ///
     /// Defaults to a gray color in the iOS color palette.
     ///
     /// This can be set to null to disable the background painting entirely; this
     /// is mildly more efficient than using [Colors.transparent].
     final Color backgroundColor;
   
     /// {@macro flutter.rendering.wheelList.offAxisFraction}
     final double offAxisFraction;
   
     /// {@macro flutter.rendering.wheelList.useMagnifier}
     final bool useMagnifier;
   
     /// {@macro flutter.rendering.wheelList.magnification}
     final double magnification;
   
     final Country initialCountry;
   
     /// A [FixedExtentScrollController] to read and control the current item.
     ///
     /// If null, an implicit one will be created internally.
     final FixedExtentScrollController scrollController;
   
     const CountryPickerCupertino({
       Key key,
       this.onValuePicked,
       this.itemBuilder,
       this.itemFilter,
       this.sortComparator,
       this.priorityList,
       this.pickerItemHeight = defaultPickerItemHeight,
       this.pickerSheetHeight = defaultPickerSheetHeight,
       this.textStyle,
       this.diameterRatio = _kDefaultDiameterRatio,
       this.backgroundColor = _kDefaultBackground,
       this.offAxisFraction = 0.0,
       this.useMagnifier = false,
       this.magnification = 1.0,
       this.scrollController,
       this.initialCountry,
     }) : super(key: key);
   
     @override
     _CupertinoCountryPickerState createState() => _CupertinoCountryPickerState();
   }
   
   class _CupertinoCountryPickerState extends State<CountryPickerCupertino> {
     List<Country> _countries;
     FixedExtentScrollController _scrollController;
   
     @override
     void initState() {
       super.initState();
   
       _countries =
           countryList.where(widget.itemFilter ?? acceptAllCountries).toList();
   
       if (widget.sortComparator != null) {
         _countries.sort(widget.sortComparator);
       }
   
       if (widget.priorityList != null) {
         widget.priorityList.forEach((Country country) =>
             _countries.removeWhere((Country c) => country.isoCode == c.isoCode));
         _countries.insertAll(0, widget.priorityList);
       }
   
       _scrollController = this.widget.scrollController;
   
       if ((_scrollController == null) && (this.widget.initialCountry != null)) {
         var countyInList = _countries
             .where((c) => c.phoneCode == this.widget.initialCountry.phoneCode)
             .first;
         _scrollController = FixedExtentScrollController(
             initialItem: _countries.indexOf(countyInList));
       }
     }
   
     @override
     Widget build(BuildContext context) {
       return _buildBottomPicker(_buildPicker(), context);
     }
   
     Widget _buildBottomPicker(Widget picker, BuildContext context) {
       var mediaQueryData = MediaQuery.of(context);
   
       return Container(
         padding: EdgeInsets.only(bottom: mediaQueryData.padding.bottom),
         height: widget.pickerSheetHeight + mediaQueryData.padding.bottom,
         child: DefaultTextStyle(
           style: widget.textStyle ??
               const TextStyle(
                 color: CupertinoColors.black,
                 fontSize: 16.0,
               ),
           child: GestureDetector(
             // Blocks taps from propagating to the modal sheet and popping.
             onTap: () {},
             child: picker,
           ),
         ),
       );
     }
   
     Widget _buildPicker() {
       return CupertinoPicker(
         scrollController: _scrollController,
         itemExtent: widget.pickerItemHeight,
         diameterRatio: widget.diameterRatio,
         backgroundColor: widget.backgroundColor,
         offAxisFraction: widget.offAxisFraction,
         useMagnifier: widget.useMagnifier,
         magnification: widget.magnification,
         children: _countries
             .map<Widget>((Country country) => widget.itemBuilder != null
                 ? widget.itemBuilder(country)
                 : _buildDefaultItem(country))
             .toList(),
         onSelectedItemChanged: (int index) {
           widget.onValuePicked(_countries[index]);
         },
       );
     }
   
     _buildDefaultItem(Country country) {
       return Padding(
         padding: const EdgeInsets.symmetric(horizontal: 8.0),
         child: Row(
           mainAxisAlignment: MainAxisAlignment.start,
           children: <Widget>[
             CountryPickerUtils.getDefaultFlagImage(country),
             SizedBox(width: 8.0),
             Flexible(child: Text(country.name))
           ],
         ),
       );
     }
   }
   
4. no-response

   removed

   waiting for responseThe Flutter team cannot make further progress on this issue until the original reporter respondsThe Flutter team cannot make further progress on this issue until the original reporter responds

   on Jun 30, 2020
5. darshankawar commented on Jun 30, 2020

   

   darshankawar

   on Jun 30, 2020

   Member

   More actions

   Hi @Faiyyaz,
   From what I can see, the issue is related to 3rd party plugin (country_pickers) rather than to Flutter itself. I see that you've already open similar issue against that plugin's repo. I'd suggest you follow-up with owner of that plugin.
   Closing, as this isn’t an issue with Flutter itself.
   If you disagree, please write in the comments,
   providing your flutter doctor -v, your flutter run -v, your pubspec.yaml
   a minimal reproducible code sample that does not use 3rd party plugins,
   and I will reopen it.
   Thank you
6. darshankawar

   closed this as completedon Jun 30, 2020
7. darshankawar

   removed

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

   on Jun 30, 2020
8. didierganthier commented on Sep 4, 2020

   

   didierganthier

   on Sep 4, 2020

   More actions

   Hi @Faiyyaz,
   From what I can see, the issue is related to 3rd party plugin (country_pickers) rather than to Flutter itself. I see that you've already open similar issue against that plugin's repo. I'd suggest you follow-up with owner of that plugin.
   Closing, as this isn’t an issue with Flutter itself.
   If you disagree, please write in the comments,
   providing your flutter doctor -v, your flutter run -v, your pubspec.yaml
   a minimal reproducible code sample that does not use 3rd party plugins,
   and I will reopen it.
   Thank you

   And don't use this plugin but I'm facing this same issue so I doubt it's related
9. 0xPixelfrost commented on Sep 30, 2020

   

   0xPixelfrost

   on Sep 30, 2020

   Last edited by 0xPixelfrost

   More actions

   Same here. The cause for this bug is, like mentioned above, the list_wheel_scroll_view.

   Following code causes the crash. minScrollExtend and maxScrollExtend are both null:
   double _clipOffsetToScrollableRange( double offset, double minScrollExtent, double maxScrollExtent, ) { return math.min(math.max(offset, minScrollExtent), maxScrollExtent); }

   I could temporary fix this by checking the line for null values like:
   double _clipOffsetToScrollableRange( double offset, double minScrollExtent, double maxScrollExtent, ) { return math.min(math.max(offset, minScrollExtent ?? 0.0), maxScrollExtent ?? 0.0); }

   I could not check the beta and dev channels due to other bugs in the framework.

   [✓] Flutter (Channel stable, 1.20.4, on Mac OS X 10.15.7 19H2, locale en-US)
       • Flutter version 1.20.4 at /Users/luckym/dev/flutter/sdk
       • Framework revision fba99f6cf9 (2 weeks ago), 2020-09-14 15:32:52 -0700
       • Engine revision d1bc06f032
       • Dart version 2.9.2
   

   Pubspec:

   environment:
     sdk: ">=2.7.0 <3.0.0"
   
   dependencies:
     flutter:
       sdk: flutter
     flutter_localizations:
       sdk: flutter
   
     async: ^2.4.1
     kt_dart: ^0.7.0+1
     freezed_annotation: ^0.12.0
   
     provider: ^4.3.2+2
     get_it: ^5.0.1
   
     logger: ^0.9.2
     flutter_svg: ^0.19.0
     transparent_image: ^1.0.0
     url_launcher: ^5.5.2
     cached_network_image: ^2.3.2+1
     cupertino_icons: ^0.1.3
   
   dev_dependencies:
     flutter_test:
       sdk: flutter
     build_runner: ^1.10.1
     freezed: ^0.12.0
     json_serializable: ^3.3.0
     pedantic: ^1.9.0
     mockito: ^4.1.1
   
   
10. bounty1342 commented on Feb 4, 2021

    

    bounty1342

    on Feb 4, 2021

    Last edited by darshankawar

    More actions

    @darshankawar, this is not related to any plugin but Cupertino Picker :

    flutter: NoSuchMethodError: The method 'toDouble' was called on null.
    Receiver: null
    Tried calling: toDouble()
    flutter: #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
    #1      double.> (dart:core-patch/double.dart:94:31)
    #2      max (dart:math-patch/math_patch.dart:43:9)
    #3      _clipOffsetToScrollableRange
    package:flutter/…/widgets/list_wheel_scroll_view.dart:364
    #4      _getItemFromOffset
    package:flutter/…/widgets/list_wheel_scroll_view.dart:356
    #5      _FixedExtentScrollPosition.itemIndex
    package:flutter/…/widgets/list_wheel_scroll_view.dart:399
    #6      _FixedExtentScrollPosition.copyWith
    package:flutter/…/widgets/list_wheel_scroll_view.dart:422
    #7      ScrollPosition.recommendDeferredLoading
    package:flutter/…/widgets/scroll_position.dart:874
    #8      Scrollable.recommendDeferredLoadingForContext
    package:flutter/…/widgets/scrollable.dart:298
    #9      ScrollAwareImageProvider.resolveStreamForKey
    package:flutter/…/widgets/scroll_aware_image_provider.dart:100
    #10     ImageProvider.resolve.<anonymous closure> (package:flutter/src/painting<…>
    flutter: NoSuchMethodError: The method 'toDouble' was called on null.
    Receiver: null
    Tried calling: toDouble()
    

    Please reopen !
11. darshankawar commented on Feb 5, 2021

    

    darshankawar

    on Feb 5, 2021

    Last edited by darshankawar

    Member

    More actions

    @bounty1342
    This is an old and closed issue. I suggest you to open a new issue and provide flutter doctor -v and minimal reproducible code sample.
12. bounty1342 commented on Feb 5, 2021

    

    bounty1342

    on Feb 5, 2021 · Hidden as off-topic

    show commentMore actions
13. darshankawar commented on Feb 5, 2021

    

    darshankawar

    on Feb 5, 2021

    Member

    More actions

    @bounty1342
    It wasn't a bot response, sorry, and if you read from my response, I requested latest flutter doctor -v and a minimal reproducible code sample that shows the issue.
14. bounty1342 commented on Feb 18, 2021

    

    bounty1342

    on Feb 18, 2021

    Last edited by bounty1342

    More actions

    flutter doctor -v

    [✓] Flutter (Channel stable, 1.22.6, on macOS 11.2.1 20D74 darwin-x64, locale en-GB)
        • Flutter version 1.22.6 at /Users/bounty1342/Documents/work/app/flutter
        • Framework revision 9b2d32b605 (4 weeks ago), 2021-01-22 14:36:39 -0800
        • Engine revision 2f0af37152
        • Dart version 2.10.5
    
    [✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
        • Android SDK at /Users/bounty1342/Library/Android/sdk
        • Platform android-30, build-tools 30.0.3
        • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
        • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)
        • All Android licenses accepted.
    
    [✓] Xcode - develop for iOS and macOS (Xcode 12.2)
        • Xcode at /Applications/Xcode.app/Contents/Developer
        • Xcode 12.2, Build version 12B45b
        • CocoaPods version 1.10.1
    
    [!] Android Studio
        • Android Studio at /Applications/Android Studio 4.2 Preview.app/Contents
        ✗ Flutter plugin not installed; this adds Flutter specific functionality.
        ✗ Dart plugin not installed; this adds Dart specific functionality.
        • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)
    
    [✓] Android Studio (version 4.1)
        • Android Studio at /Applications/Android Studio.app/Contents
        • Flutter plugin installed
        • Dart plugin version 201.9317
        • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)
    
    [✓] VS Code (version 1.53.2)
        • VS Code at /Applications/Visual Studio Code.app/Contents
        • Flutter extension version 3.19.0
    
    [✓] Connected device (2 available)
        • sdk google atv x86 (mobile) • emulator-5554                        • android-x86 • Android 10 (API 29) (emulator)
        • iPhone 12 Pro Max (mobile)  • 7FC20A84-7B08-43AA-BF0C-E183104B503B • ios         • com.apple.CoreSimulator.SimRuntime.iOS-14-2 (simulator)
    
    ! Doctor found issues in 1 category.
    

    Issue found

    ════════ Exception caught by image resource service ════════════════════════════
    The following NoSuchMethodError was thrown while resolving an image:
    The method 'toDouble' was called on null.
    Receiver: null
    Tried calling: toDouble()
    
    When the exception was thrown, this was the stack
    #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
    #1      double.> (dart:core-patch/double.dart:94:31)
    #2      max (dart:math-patch/math_patch.dart:43:9)
    #3      _clipOffsetToScrollableRange
    package:flutter/…/widgets/list_wheel_scroll_view.dart:364
    #4      _getItemFromOffset
    package:flutter/…/widgets/list_wheel_scroll_view.dart:356
    ...
    Image provider: ScrollAwareImageProvider<dynamic>()
    Image configuration: ImageConfiguration(bundle: PlatformAssetBundle#94b6e(), devicePixelRatio: 3.0, locale: en_US, textDirection: TextDirection.ltr, platform: iOS)
    Image key: NetworkImage("https://e7.pngegg.com/pngimages/595/79/png-clipart-dart-programming-language-flutter-object-oriented-programming-flutter-logo-class-fauna-thumbnail.png", scale: 1.0)
    ════════════════════════════════════════════════════════════════════════════════
    
    ════════ Exception caught by image resource service ════════════════════════════
    The method 'toDouble' was called on null.
    Receiver: null
    Tried calling: toDouble()
    ════════════════════════════════════════════════════════════════════════════════
    
    

    minimal reproducible code sample

    import 'package:flutter/cupertino.dart';
    import 'package:flutter/material.dart';
    
    void main() => runApp(MyApp());
    
    const url =
        "https://e7.pngegg.com/pngimages/595/79/png-clipart-dart-programming-language-flutter-object-oriented-programming-flutter-logo-class-fauna-thumbnail.png";
    
    class MyApp extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          title: 'Flutter Demo',
          theme: ThemeData(
            primarySwatch: Colors.blue,
          ),
          home: MyHomePage(),
        );
      }
    }
    
    class MyHomePage extends StatefulWidget {
      @override
      _MyHomePageState createState() => _MyHomePageState();
    }
    
    class _MyHomePageState extends State<MyHomePage> {
      FixedExtentScrollController _controller;
      int _currentIndex;
    
      @override
      void initState() {
        super.initState();
        _currentIndex = 0;
        _controller = FixedExtentScrollController(
          initialItem: _currentIndex,
        );
      }
    
      @override
      void dispose() {
        _controller.dispose();
        super.dispose();
      }
    
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          appBar: AppBar(
            title: Text("ScrollWheel"),
          ),
          body: SingleChildScrollView(
              child: Container(
            height: MediaQuery.of(context).size.height,
            width: MediaQuery.of(context).size.width,
            child: CupertinoPicker.builder(
              scrollController: _controller,
              offAxisFraction: 0.0,
              itemExtent: 80,
              childCount: 20,
              useMagnifier: true,
              magnification: 1.1,
              diameterRatio: 0.5,
              backgroundColor: Colors.red,
              onSelectedItemChanged: (value) {
                setState(() {
                  print(value);
                });
              },
              itemBuilder: (context, index) =>
                  SizedBox(height: 80, child: Center(child: Image.network(url))),
            ),
          )),
        );
      }
    }
    

    Screenshot of issue :	Expected screenshot (with #60578 (comment)):

    @darshankawar : Sorry, really thought it was. I did everything you asked for, so please reopen and take care of it.
15. 17 remaining items

    Load more

16. hyungtaecf commented on May 19, 2021

    

    hyungtaecf

    on May 19, 2021

    More actions

    Still reproducible in 2.0.6
    Is there at least a workaround?

    I don't know if it is applicable to your context, but I mentioned my workaround here #61228, that is very simple but it took me a lot of time to find it... Now it works fine for me.

    I was trying to fix the issue for my app for hours! I tried a lot of stuff, and I decided to try one last stupid thing before giving up, but it ended up working in my case!!

    I'm using FancyShimmerImage inside ListWheelScrollView, which is basically the CachedNetworkImage with a shimmer. I noticed the problem was only happening to me for the visible widgets in the ListWheelScrollView, but when scrolling to the parts where it starts hidden, those images were loading well. So I realized it happens just in the first rendering. Then I had what I thought was a stupid idea, that I set the errorWidget to be displayed in the CachedNetworkImage as the FancyShimmerImage itself, and it ended up that when it tries to load the image again it works.

    👍React with 👍1Reacted by in-nizam-cs
17. bounty1342 commented on May 19, 2021

    

    bounty1342

    on May 19, 2021

    More actions

    The issue is due to the widget having no size. (loading a Network images for example)
    A placeolder with a size should avoid this issue.

    👍React with 👍1Reacted by rockingdice
18. rockingdice commented on May 21, 2021

    

    rockingdice

    on May 21, 2021

    More actions

    Met the same issue. Please solve it asap. I'm using CupertinoPicker and can reproduce this issue.
19. rockingdice commented on May 21, 2021

    

    rockingdice

    on May 21, 2021

    Last edited by rockingdice

    More actions

    FYI, I found a workaround:
    Use a FutureBuilder. You can wrap your widget into it and it will show without the exception.
    You might consider using a SynchronousFuture to make it not blink.

    In the mean time we might expect the flutter team to fix it.
20. Levi-Lesches commented on Aug 13, 2021

    

    Levi-Lesches

    on Aug 13, 2021

    Contributor

    More actions

    Now that the error has changed, I think this became a duplicate of #85867, which has less discussion. Or that is a duplicate of this, but one of them can be closed.
21. goderbauer

    added

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

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

    on Aug 16, 2022
22. bleroux commented on Nov 29, 2022

    

    bleroux

    on Nov 29, 2022

    Contributor

    More actions

    This issue is no more reproducible since Flutter 3.0.5.
    Closing it as fixed by #96102 (found using git bisect).
23. bleroux

    closed this as completedon Nov 29, 2022
24. bleroux

    added

    r: fixedIssue is closed as already fixed in a newer versionIssue is closed as already fixed in a newer version

    on Nov 29, 2022
25. bleroux

    added this to Nevercodeon Nov 30, 2022
26. bleroux

    moved this to To do in Nevercodeon Nov 30, 2022
27. bleroux

    moved this from To do to Issue closed with comment in Nevercodeon Nov 30, 2022
28. github-actions commented on Mar 5, 2023

    

    github-actionsBot

    on Mar 5, 2023

    More actions

    This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
29. github-actions

    locked as resolved and limited conversation to collaborators on Mar 5, 2023