ScrollController _scrollController;
@override
  void initState() {
    _scrollController = ScrollController(keepScrollOffset: true);
    super.initState();
ListView.builder(
                          controller: _scrollController,
                          itemCount: snapshot?.data?.length ?? 0,
                            itemBuilder: (context, index) => Container(
                              decoration: BoxDecoration(
                                color: kColor_white,
                                borderRadius: BorderRadius.circular(6),
                                border: Border.all(width: 1, color: kColor_white),
Error I am getting
> E/flutter ( 9253): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: 'package:flutter/src/widgets/scroll_controller.dart': Failed assertion: line 110 pos 12: '_positions.isNotEmpty': ScrollController not attached to any scroll views.
E/flutter ( 9253): #0      _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:40:39)
E/flutter ( 9253): #1      _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter ( 9253): #2      ScrollController.position (package:flutter/src/widgets/scroll_controller.dart:110:12)
E/flutter ( 9253): #3      ScrollController.offset (package:flutter/src/widgets/scroll_controller.dart:118:24)
E/flutter ( 9253): #4      PostsListState._fetchPosts.<anonymous closure> (package:wakwat/src/screens/posts/posts_list.dart:148:57)
E/flutter ( 9253): #5      _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter ( 9253): #6      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter ( 9253): #7      _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter ( 9253): #8      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter ( 9253): #9      Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter ( 9253): #10     Future._complete (dart:async/future_impl.dart:473:7)
E/flutter ( 9253): #11     _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter ( 9253): #12     _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:28:18)
E/flutter ( 9253): #13     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:294:13)
E/flutter ( 9253): #14     getPosts (package:wakwat/api/get_services/posts_service.dart)
E/flutter ( 9253): <asynchronous suspension>
E/flutter ( 9253): #15     PostsListState._fetchPosts (package:wakwat/src/screens/posts/posts_list.dart:119:20)
E/flutter ( 9253): <asynchronous suspension>
E/flutter ( 9253): #16     PostsListState.initState (package:wakwat/src/screens/posts/posts_list.dart:56:5)
E/flutter ( 9253): #17     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3846:58)
E/flutter ( 9253): #18     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3717:5)
E/flutter ( 9253): #19     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter ( 9253): #20     Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter ( 9253): #21     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4876:14)
E/flutter ( 9253): #22     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter ( 9253): #23     Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter ( 9253): #24     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4876:14)
E/flutter ( 9253): #25     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter ( 9253): #26     Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter ( 9253): #27     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3750:16)
E/flutter ( 9253): #28     Element.rebuild (package:flutter/src/widgets/framework.dart:3565:5)
E/flutter ( 9253): #29     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3722:5)
E/flutter ( 9253): #30     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3717:5)
E/flutter ( 9253): #31     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter ( 9253): #32     Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter ( 9253): #33     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3750:16)
E/flutter ( 9253): #34     Element.rebuild (package:flutter/src/widgets/framework.dart:3565:5)
E/flutter ( 9253): #35     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3722:5)
E/flutter ( 9253): #36     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3717:5)
E/flutter ( 9253): #37     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:4063:11)
E/flutter ( 9253): #38     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter ( 9253): #39     Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter ( 9253): #40     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3750:16)
E/flutter ( 9253): #41     Element.rebuild (package:flutter/src/widgets/framework.dart:3565:5)
E/flutter ( 9253): #42     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3722:5)
E/flutter ( 9253): #43     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3864:11)
E/flutter ( 9253): #44     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3717:5)
E/flutter ( 9253): #45     Element.inflateWidget (package:flutter/sr
Here is the flutter doctor Output:
/home/maximus/flutter/bin/flutter doctor --verbose
[✓] Flutter (Channel stable, v1.5.4-hotfix.2, on Linux, locale en_IN)
• Flutter version 1.5.4-hotfix.2 at /home/maximus/flutter
• Framework revision 7a4c334 (5 weeks ago), 2019-04-29 11:05:24 -0700
• Engine revision 52c7a1e849
• Dart version 2.3.0 (build 2.3.0-dev.0.5 a1668566e5)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /home/maximus/Android/Sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-28, build-tools 28.0.3
• Java binary at: /home/maximus/Documents/android-studio/jre/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b16-5323222)
• All Android licenses accepted.
[✓] Android Studio (version 3.4)
• Android Studio at /home/maximus/Documents/android-studio
• Flutter plugin version 35.3.1
• Dart plugin version 183.6270
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b16-5323222)
[✓] Connected device (1 available)
• Android SDK built for x86 • emulator-5554 • android-x86 • Android 9 (API 28) (emulator)
• No issues found!
          
Facing the same issue when having 2 ScrollController in a 2 tab view screen, where each controller is attached to one tab respectively and i get this error when switching tabs
flutter: Error caught by animation library, thrown while notifying listeners for AnimationController.
ScrollController not attached to any scroll views.
'package:flutter/src/widgets/scroll_controller.dart': Failed assertion: line 110 pos 12: '_positions.isNotEmpty'
The AnimationController notifying listeners was:
  AnimationController#34976(▶ 163.118; for DrivenScrollActivity)#2      ScrollController.position 
package:flutter/…/widgets/scroll_controller.dart:110
#3      ScrollController.offset 
package:flutter/…/widgets/scroll_controller.dart:118
#4      _FacilityPracticeScreenState.build.<anonymous closure>.<anonymous closure> 
package:loop/screens/health_system_screen.dart:196
#5      State.setState 
package:flutter/…/widgets/framework.dart:1117
#6      _FacilityPracticeScreenState.build.<anonymous closure> 
package:loop/screens/health_system_screen.dart:195
#7      NotificationListener._dispatch 
package:flutter/…/widgets/notification_listener.dart:127
#8      Notification.visitAncestor 
package:flutter/…/widgets/notification_listener.dart:45
#9      _ScrollNotification&LayoutChangedNotification&ViewportNotificationMixin.visitAncestor 
package:flutter/…/widgets/scroll_notification.dart:31
#10     Element.visitAncestorElements 
package:flutter/…/widgets/framework.dart:3355
#11     Notification.dispatch 
package:flutter/…/widgets/notification_listener.dart:61
#12     ScrollActivity.dispatchScrollUpdateNotification 
package:flutter/…/widgets/scroll_activity.dart:96
#13     ScrollPosition.didUpdateScrollPositionBy 
package:flutter/…/widgets/scroll_position.dart:658
#14     ScrollPosition.setPixels 
package:flutter/…/widgets/scroll_position.dart:219
#15     ScrollPositionWithSingleContext.setPixels 
package:flutter/…/widgets/scroll_position_with_single_context.dart:84
#16     DrivenScrollActivity._tick 
package:flutter/…/widgets/scroll_activity.dart:629
#17     _AnimationController&Animation&AnimationEagerListenerMixin&AnimationLocalListenersMixin.notifyListeners 
package:flutter/…/animation/listener_helpers.dart:126
#18     AnimationController._tick 
package:flutter/…/animation/animation_controller.dart:750
#19     Ticker._tick 
package:flutter/…/scheduler/ticker.dart:228
#20     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback 
package:flutter/…/scheduler/binding.dart:1012
#21     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame.<anonymous closure> 
package:flutter/…/scheduler/binding.dart:928
#22     __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.forEach  (dart:collection-patch/compact_hash.dart:367:8)
#23     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleBeginFrame 
package:flutter/…/scheduler/binding.dart:926
#24     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleBeginFrame 
package:flutter/…/scheduler/binding.dart:856
#28     _invoke1  (dart:ui/hooks.dart:233:10)
#29     _beginFrame  (dart:ui/hooks.dart:172:3)
          
the same error




    

I/flutter ( 6725): The following assertion was thrown while handling a gesture:
I/flutter ( 6725): ScrollController not attached to any scroll views.
I/flutter ( 6725): 'package:flutter/src/widgets/scroll_controller.dart':
I/flutter ( 6725): Failed assertion: line 110 pos 12: '_positions.isNotEmpty'
I/flutter ( 6725):
I/flutter ( 6725): Either the assertion indicates an error in the framework itself, or we should provide substantially
I/flutter ( 6725): more information in this error message to help you determine and fix the underlying cause.
I/flutter ( 6725): In either case, please report this assertion by filing a bug on GitHub:
I/flutter ( 6725):   https://github.com/flutter/flutter/issues/new?template=BUG.md
the same error
E/flutter (25839): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: 'package:flutter/src/widgets/scroll_controller.dart': Failed assertion: line 110 pos 12: '_positions.isNotEmpty': ScrollController not attached to any scroll views.
E/flutter (25839): #0      _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:40:39)
E/flutter (25839): #1      _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter (25839): #2      ScrollController.position (package:flutter/src/widgets/scroll_controller.dart:110:12)
E/flutter (25839): #3      PageController.animateToPage (package:flutter/src/widgets/page_view.dart:202:41)
E/flutter (25839): #4      _HomeState._loopBanner (package:gank_flutter/pages/home.dart:140:21)
E/flutter (25839): #5      _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (25839): #6      _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (25839): #7      _CustomZone.runUnaryGuarded (dart:async/zone.dart:931:7)
E/flutter (25839): #8      _CustomZone.bindUnaryCallbackGuarded.<anonymous closure> (dart:async/zone.dart:968:26)
E/flutter (25839): #9      _rootRunUnary (dart:async/zone.dart:1136:13)
E/flutter (25839): #10     _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (25839): #11     _CustomZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:952:26)
E/flutter (25839): #12     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
E/flutter (25839): #13     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
E/flutter (25839): #14     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
I had this problem in my project. I solved it upgrading flutter. 1.9.1+hotfix.6 (Linux) worked fine.
I do have the same version and I am facing the same issue...
In my case is happening when  trying to change scroll position during widget build function. Changing scroll position with a delay of 200ms solved my problem...
          
Any updates on this, seems like this crashes app in production.
 Scaffold(
        body: NotificationListener(
            onNotification: (scroll) {
              if (scroll is ScrollUpdateNotification) {
                if (mounted)
                  setState(() {
                    clipVal = _tabController.index == 0
                        ? incomingController?.offset?.floorToDouble() ?? 0.0
                        : outgoingController?.offset?.floorToDouble() ?? 0.0;
          
Delaying it is not the right solution. Better to wait till the tree is done building by using
SchedulerBinding.instance.addPostFrameCallback((_) {
      if (scrollController.hasClients) {
        scrollController.animateTo(
          scrollController.position.maxScrollExtent,
          curve: Curves.easeOut,
          duration: const Duration(milliseconds: 200),
          
Doctor summary (to see all details, run flutter doctor -v):

[✓] Flutter (Channel beta, v1.12.13+hotfix.6, on Mac OS X 10.15.1 19B2093,

locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)

[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)

[✓] Chrome - develop for the web

[✓] Android Studio (version 3.5)

[✓] Connected device (3 available)
Repo : https://github.com/theindianappguy/app_onboarding
@Piinks  please check
          
Hi @theindianappguy thanks for the update! Can you provide a minimal runnable reproduction? The project you linked to makes it hard to diagnose the issue. From our issue hygiene guide, the best way to diagnose this is to provide a sample that has been reduced as far as possible (such that removing anything further stops showing the bug)
          
Wrapping the animateTo in an if (_scrollController.hasClients) worked for me.
if (_scrollController.hasClients) {

_scrollController.animateTo(

_scrollController.position.minScrollExtent,

duration: const Duration(milliseconds: 1),

curve: Curves.easeOut);

          
I am getting this issue too, maybe mine is a naive approach.

Below is the exception details :

I/flutter ( 7970): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════ I/flutter ( 7970): The following assertion was thrown while handling a gesture: I/flutter ( 7970): ScrollController not attached to any scroll views. I/flutter ( 7970): 'package:flutter/src/widgets/scroll_controller.dart': I/flutter ( 7970): Failed assertion: line 110 pos 12: '_positions.isNotEmpty' I/flutter ( 7970):  I/flutter ( 7970): Either the assertion indicates an error in the framework itself, or we should provide substantially I/flutter ( 7970): more information in this error message to help you determine and fix the underlying cause. I/flutter ( 7970): In either case, please report this assertion by filing a bug on GitHub: I/flutter ( 7970):   https://github.com/flutter/flutter/issues/new?template=BUG.md I/flutter ( 7970):  I/flutter ( 7970): When the exception was thrown, this was the stack: I/flutter ( 7970): #2      ScrollController.position (package:flutter/src/widgets/scroll_controller.dart:110:12) I/flutter ( 7970): #3      HomePageState.build.<anonymous closure> (package:flutter_app/main.dart:98:43) I/flutter ( 7970): #4      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:706:14) I/flutter ( 7970): #5      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:789:36) I/flutter ( 7970): #6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24) I/flutter ( 7970): #7      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:486:11) I/flutter ( 7970): #8      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:264:5) I/flutter ( 7970): #9      BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:199:7) I/flutter ( 7970): #10     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:467:9) I/flutter ( 7970): #11     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:76:12) I/flutter ( 7970): #12     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:117:9) I/flutter ( 7970): #13     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8) I/flutter ( 7970): #14     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:115:18) I/flutter ( 7970): #15     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:7) I/flutter ( 7970): #16     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:218:19) I/flutter ( 7970): #17     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22) I/flutter ( 7970): #18     GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7) I/flutter ( 7970): #19     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7) I/flutter ( 7970): #20     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7) I/flutter ( 7970): #24     _invoke1 (dart:ui/hooks.dart:273:10) I/flutter ( 7970): #25     _dispatchPointerDataPacket (dart:ui/hooks.dart:182:5) I/flutter ( 7970): (elided 5 frames from class _AssertionError and package dart:async) I/flutter ( 7970):  I/flutter ( 7970): Handler: "onTap" I/flutter ( 7970): Recognizer: I/flutter ( 7970):   TapGestureRecognizer#c2341 I/flutter ( 7970): ════════════════════════════════════════════════════════════════════════════════════════════════════ I/flutter ( 7970): Another exception was thrown: ScrollController not attached to any scroll views.
and main.dart (only) file is

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {

@OverRide

Widget build(BuildContext context) {

return new MaterialApp(

home: new HomePage(),

theme: new ThemeData(

primarySwatch: Colors.blue, brightness: Brightness.light),

class HomePage extends StatefulWidget {

@OverRide

State createState() => new HomePageState();

class HomePageState extends State {

int count = 0;

ScrollController _scrollController = ScrollController();

List txtForms;
@OverRide

void initState() {

super.initState();

txtForms = [];

txtForms.add(createTextFormField());

txtForms.add(createTextFormField());

txtForms.add(createTextFormField());

createTextFormField() {

count += 1;

return TextFormField(

decoration: new InputDecoration(labelText: "Enter item $count"),

keyboardType: TextInputType.text,

@OverRide

Widget build(BuildContext context) {

return Scaffold(

appBar: AppBar(),

body: Column(

children: [

Padding(

padding: EdgeInsets.symmetric(vertical: 32.0),

child: MaterialButton(

child: Text("Upload"),

color: Colors.blue,

minWidth: 180.0,

onPressed: () {})),

Text('Or'),

Expanded(

child: Column(

children: [

Expanded(

child: ListView.builder(

itemCount: txtForms.length,

itemBuilder: (context, index) {

return Row(

children: [

SizedBox(

child: txtForms[index],

width:

MediaQuery.of(context).size.width - 80.0,

IconButton(

color: Colors.grey,

onPressed: () {

setState(() {

txtForms.removeAt(index);

_scrollController.animateTo(

_scrollController

.position.maxScrollExtent,

duration:

const Duration(milliseconds: 50),

curve: Curves.easeOut,

icon: Icon(Icons.delete),

MaterialButton(

child: Text("Add more items"),

splashColor: Colors.blueAccent,

onPressed: () {

setState(() {

txtForms.add(createTextFormField());

_scrollController.animateTo(

_scrollController.position.maxScrollExtent,

duration: const Duration(milliseconds: 50),

curve: Curves.easeOut,

Padding(

padding: EdgeInsets.symmetric(vertical: 32.0),

child: MaterialButton(

color: Colors.blue,

child: Text("Submit"),

minWidth: 180.0,

onPressed: () => {},

andflutter doctor -vshows

[✓] Flutter (Channel stable, v1.12.13+hotfix.8, on Linux, locale en_IN)

• Flutter version 1.12.13+hotfix.8 at /home/rrj/flutter

• Framework revision 0b8abb4 (4 weeks ago), 2020-02-11 11:44:36 -0800

• Engine revision e1e6ced

• Dart version 2.7.0

[!] Android toolchain - develop for Android devices (Android SDK version 29.0.3)

• Android SDK at /home/rrj/Android/Sdk

• Android NDK location not configured (optional; useful for native profiling

support)

• Platform android-29, build-tools 29.0.3

• Java binary at: /usr/local/android-studio/jre/bin/java

• Java version OpenJDK Runtime Environment (build

1.8.0_212-release-1586-b4-5784211)

! Some Android licenses not accepted.  To resolve this, run: flutter doctor

--android-licenses

[✓] Android Studio (version 3.6)

• Android Studio at /usr/local/android-studio

• Flutter plugin version 44.0.2

• Dart plugin version 192.7761

• Java version OpenJDK Runtime Environment (build

1.8.0_212-release-1586-b4-5784211)

[✓] VS Code (version 1.42.1)

• VS Code at /usr/share/code

• Flutter extension version 3.8.1

[✓] Connected device (1 available)

• AOSP on IA Emulator • emulator-5554 • android-x86 • Android 9 (API 28)

(emulator)

! Doctor found issues in 1 category.

and I am trying to debug this code on the image of Pixel_2_API_28

after pressing Add more item section I wanted to show the latest inserted items in that visible area of ListView.builder. Maybe in another way of implementation can be achieved easily but this way I was getting the above exception.
          
My issue is happened when I tried to use CupertinoScrollbar() with displayAlways: true without controller in SingleChildScrollView() ...
This works fine:

        child: CupertinoScrollbar(
          child: SingleChildScrollView(
this too:
  final ScrollController scrollController = ScrollController();
        child: CupertinoScrollbar(
          controller: scrollController,
          child: SingleChildScrollView(
            controller: scrollController,
but when I used displayAlways: true in CupertinoScrollbar() then to set controller in both widgets was necessary:
  final ScrollController scrollController = ScrollController();
        child: CupertinoScrollbar(
          displayAlways: true,
          controller: scrollController,
          child: SingleChildScrollView(
            controller: scrollController,
Issue occurred with this code:
  final ScrollController scrollController = ScrollController();
        child: CupertinoScrollbar(
          displayAlways: true,
          controller: scrollController,
          child: SingleChildScrollView(
// no controller is set
But I use not released flutter/packages/flutter/lib/src/cupertino/scrollbar.dart from not merged branch...
Update your Flutter SDK it will solve this problem

that is work for me

Run this on your cmd - flutter update
Which Flutter version will fix this?

Having the same problem.
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.12.13+hotfix.9, on Mac OS X 10.15.4 19E287, locale de-DE)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.0-rc2)
[✓] Xcode - develop for iOS and macOS (Xcode 11.4)
[✓] Android Studio (version 3.6)
[✓] VS Code (version 1.43.2)
[✓] Connected device (2 available)
• No issues found!