当items 为空或者items.length =0 时有问题，

[liaoli]

The method '_addFromInteger' was called on null.
Receiver: null
Tried calling: _addFromInteger(1)

The relevant error-causing widget was:
ExampleListView file:///Users/mac/Downloads/flutter_sticky_and_expandable_list-master/example/lib/main.dart:43:50
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1 int.+ (dart:core-patch/integers.dart:12:38)
#2 SliverExpandableChildDelegate._buildSectionRealIndexes (package:sticky_and_expandable_list/src/sliver_expandable_list.dart:214:22)
#3 new SliverExpandableChildDelegate (package:sticky_and_expandable_list/src/sliver_expandable_list.dart:81:30)
#4 _ExampleListViewState.build (package:example/example_listview.dart:18:20)

[tp7309]

需要确保传入的sectionList中的每个section不为空，section.getItems()为空应该是没问题的。

[liaoli]

section.getItems()为空或者 length =0 的确有问题

realIndex += 1 + section.getItems()?.length ?? 0;
改成
int value = section.getItems()?.length ?? 0;
realIndex += 1 + value;
就可以了

[tp7309]

按说是等价的才对，难道有运算符优先级问题？晚上回去看看。

[tp7309]

已处理，感谢反馈。