FlutterException: Null check operator used on a null value

[LGang]

Stack:

#0      RenderSliverStack.performLayout (package:sliver_tools/src/rendering/sliver_stack.dart:190)
#1      RenderObject.layout (package:flutter/src/rendering/object.dart:1915)
#2      RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:510)
#3      RenderViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1580)
#4      RenderViewport.performLayout (package:flutter/src/rendering/viewport.dart:1489)
#5      RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1757)
#6      PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:887)
#7      RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:504)
#8      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:892)
#9      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:370)
#10     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1146)
#11     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1083)
#12     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:997)
#13     _rootRun (dart:async/zone.dart:1426)
#14     _CustomZone.run (dart:async/zone.dart:1328)
#15     _CustomZone.runGuarded (dart:async/zone.dart:1236)
#16     _invoke (dart:ui/hooks.dart:151)
#17     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:308)
#18     _drawFrame (dart:ui/hooks.dart:115)

[Kavantix]

@LGang can you add some more information on what and when you run into this exception?

[LGang]

@LGang can you add some more information on what and when you run into this exception?

Online logs are reported up and cannot be reproduced

[LGang]

Partial code

LoadingMoreCustomScrollView(
                controller: controller.scrollController,
                physics: const ClampingScrollPhysics(),
                cacheExtent: 800,
                slivers: <Widget>[
                  SliverPersistentHeader(
                    delegate: PlaceholderPersistentHeaderDelegate(
                        child: _buildTabBar(0)),
                    floating: true,
                  ),
                  SliverPersistentHeader(
                    delegate: PersistentHeaderDelegate(
                      child: Obx(() => _buildOrderMenu(controller.orderMenus)),
                    ),
                    pinned: true,
                  ),
                  Obx(() => controller.categoryList.isNotEmpty
                      ? SliverToBoxAdapter(
                          child: _buildRecommendSubType(),
                        )
                      : const SliverToBoxAdapter()),
                  SliverStack(
                    children: [
                      SliverPositioned(
                        child: Container(
                          height: 192,
                          decoration: const BoxDecoration(
                            gradient: LinearGradient(
                              begin: Alignment.topCenter,
                              end: Alignment.bottomCenter,
                              colors: [
                                Colors.white,
                                Color(0xFFF7F8FA),
                              ],
                            ),
                          ),
                        ),
                        left: 0,
                        right: 0,
                        top: 0,
                        height: 192,
                      ),
                      Obx(
                        () => LoadingMoreSliverList<GoodsCardModel>(
                          SliverListConfig<GoodsCardModel>(
                            itemBuilder: (BuildContext context,
                                GoodsCardModel viewModel, int index) {
                              return _buildListitemView(viewModel, index);
                            },
                            sourceList: controller.repository,
                            padding: !controller.gridLayout.value
                                ? EdgeInsets.zero
                                : const EdgeInsets.only(
                                    left: 12, right: 12, top: 4),
                            extendedListDelegate: !controller.gridLayout.value
                                ? null
                                : const SliverWaterfallFlowDelegateWithMaxCrossAxisExtent(
                                    maxCrossAxisExtent: 300,
                                    crossAxisSpacing: 7,
                                    mainAxisSpacing: 7,
                                  ),
                          ),
                        ),
                      ),
                    ],
                  ),
                ],
              )

[Kavantix]

Which version of sliver_tools are you using?

[LGang]

Which version of sliver_tools are you using?

0.2.7

[Kavantix]

@LGang I'v taken a look at what is crashing.
This error means that a sliver child of the SliverStack did not set its geometry after layout, that's not a good thing and not a fault of this package.

I'll add an assert for this case in an upcoming release though!