BottomSheetRoute throws if declared as initial route

[tomwyr]

I am using modal_bottom_sheet together with auto_route package. My routes declaration looks more or less like this:

@MaterialAutoRouter(
  routes: [
    AutoRoute(
      path: '/',
      page: EmptyRouterPage,
      name: 'RootRoute',
      children: [
        AutoRoute(
          initial: true,
          page: HomePage,
        ),
        CustomRoute(
          page: EmptyRouterPage,
          name: 'OtherFlowRoute',
          children: [
            CustomRoute(
              initial: true,
              page: EmptyRouterPage,
              name: 'BottomSheetRoute',
              customRouteBuilder: buildModalBottomSheetRoute,
              children: [
                // ... bottom sheet routes
              ],
            ),
            // ... other flow routes
          ],
        ),
      ],
    ),
  ],
)

When I try to navigate to other flow and push modal bottom sheet as the initial route, I get following error:

════════ Exception caught by widgets library ═══════════════════════════════════
The following _CastError was thrown building WillPopScope(dependencies: [_ModalScopeStatus], state: _WillPopScopeState#2ab01):
Null check operator used on a null value

The relevant error-causing widget was
AutoRouter
lib/widgets.dart:36
When the exception was thrown, this was the stack
#0      ModalBottomSheetRoute.createAnimationController
package:modal_bottom_sheet/src/bottom_sheet_route.dart:176
#1      TransitionRoute.install
package:flutter/…/widgets/routes.dart:220
#2      ModalRoute.install
package:flutter/…/widgets/routes.dart:1146
#3      _RouteEntry.handleAdd
package:flutter/…/widgets/navigator.dart:2818
#4      NavigatorState._flushHistoryUpdates
package:flutter/…/widgets/navigator.dart:3813
#5      NavigatorState.restoreState
package:flutter/…/widgets/navigator.dart:3318
#6      RestorationMixin._doRestore
package:flutter/…/widgets/restoration.dart:887
#7      RestorationMixin.didChangeDependencies
package:flutter/…/widgets/restoration.dart:873
#8      NavigatorState.didChangeDependencies
package:flutter/…/widgets/navigator.dart:3336
#9      StatefulElement._firstBuild
package:flutter/…/widgets/framework.dart:4914
#10     ComponentElement.mount
package:flutter/…/widgets/framework.dart:4729
// more stack trace

This is because ModalBottomSheet attempts to create animation controller before first frame in which case overlay is still unavailable.
https://github.com/jamesblasco/modal_bottom_sheet/blob/master/lib/src/bottom_sheet_route.dart#L176
Is there any specific reason to use overlay as TickerProvider? E.g. bottom sheet from the SDK simply uses navigator to create the controller:
https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/material/bottom_sheet.dart#L513

Let me know if I could provide any additional info that would be helpful.

[mrhabibi]

Any update on this? In my case, this was happened when my app was restoring state and the bottom sheet was in the top of the navigation stack.

[guenth39]

Same issue. Any update on this?

[janknips]

Same issue here unfortunately

[pgulegin]

Having this issue as well.

[taiseidev]

Same issue.

[talhakerpicci]

Same issue here

[vasilich6107]

Hi.
The issue is on this line

modal_bottom_sheet/modal_bottom_sheet/lib/src/bottom_sheet_route.dart

Line 183 in 3917484

navigator!.overlay!,

just put navigator! instead navigator!.overlay and it should work

[kvenn]

It looks like that's what they do in Flutter ModalBottomSheetRoute.

  @override
  AnimationController createAnimationController() {
    assert(_animationController == null);
    if (transitionAnimationController != null) {
      _animationController = transitionAnimationController;
      willDisposeAnimationController = false;
    } else {
      _animationController = BottomSheet.createAnimationController(navigator!);
    }
    return _animationController!;
  }

I opened a PR with that change: #379