颤振将变量传递给 SearchDelegate 类给出错误

Question

我是一个新手，我在将数据传递给我的搜索委托类时遇到问题。问题是我有两个标签，我想在活动标签中搜索。所以我试图发送一个变量来告诉它是哪个选项卡以及要在哪个表中查找值。

我的代码如下所示：

    class HomePage extends StatefulWidget {
                  static final String routeName = 'home';

                  @override
                  State<StatefulWidget> createState() {
                    return new _HomePageState();
                  }
                }

                class _HomePageState extends State<HomePage> with TickerProviderStateMixin {

                  var activeTab = "activity";

                  var _authToken, _id, _name, _emails, _userImage;

                  @override
                  void initState() {
                    super.initState();
                    tabController = TabController(vsync: this, length: 2)..addListener(() {
                        setState(() {
                          switch (tabController.index) {
                            case 0:
                              activeTab = "activity";
                              break;
                            case 1:
                              activeTab = "subparticipants";
                              break;
                          }
                        });
                      });
                  }



                  @override
                  Widget build(BuildContext context) {
                    return new Scaffold(
                      key: _scaffoldKey,
                      // appBar: new AppBar(
                      //   title: Text('Dashboard'),
                      // ),
                      body: DefaultTabController(
                        length: 2,
                        child: Scaffold(
                          appBar: AppBar(
                            bottom: TabBar(
                              labelColor: Color(0xFFFFFFFF),
                              indicatorSize: TabBarIndicatorSize.tab,
                              tabs: [
                                //Tab(icon: Icon(Icons.directions_car)),
                                Tab(
                                  text: "Activity Zone",
                                ),
                                Tab(
                                  text: "Sub Participant",
                                )
                              ],
                              controller: tabController,
                            ),
                            title: Text(
                              'Dashboard',
                              style: new TextStyle(
                                color: const Color(0xFFFFFFFF),
                                fontSize: 20.0,
                                fontWeight: FontWeight.w600,
                                letterSpacing: 0.3,
                              ),
                            ),
                            actions: <Widget>[
                              IconButton(
                                icon: Icon(Icons.search),
                                onPressed: () {
                                  showSearch(context: context, delegate: DataSearch(activeTab));
                                },
                              )
                            ],
                          ),
                          body: TabBarView(
                            controller: tabController,
                            children: [
                              TabActivity(),
                              TabSubparticipant(),
                            ],
                          ),
                          floatingActionButton: FloatingActionButton(
                              onPressed: () {
                                print(
                                    'Current Index: $activeTab');
                              },
                            ),
                          drawer: _buildDrawer(context),
                        ),
                      ),
                    );
                  }
                }
     class DataSearch extends SearchDelegate{
              final String activeTab;
              DataSearch(this.activeTab);

              @override
              List<Widget> buildActions(BuildContext context){
                return [
                  IconButton(
                    icon: Icon(Icons.arrow_back),
                    onPressed: (){
                      query=activeTab;
                    },
                  )
                ];
              }

              @override
              Widget buildLeading(BuildContext context) => IconButton(
                    icon: Icon(Icons.close),
                    onPressed: () => Navigator.of(context).pop(),
                  );

              @override
              Widget buildResults(BuildContext context) => Text('Result');

              @override
              Widget buildSuggestions(BuildContext context) {
                return Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Text(
                    'Search by job id, asset name, client name $query',
                    style: new TextStyle(
                        color: Colors.black, fontWeight: FontWeight.bold, fontSize: 22.0),
                  ),
                );
              }
            }

当我尝试获取 $activeTab 并在查询或其他地方显示它时，它只会给出错误：

flutter: The following assertion was thrown building _SearchPage<dynamic>(dirty, dependencies:
flutter: [_LocalizationsScope-[GlobalKey#a02e3], _InheritedTheme], state: _SearchPageState<dynamic>#eceaa):
flutter: 'package:flutter/src/widgets/basic.dart': Failed assertion: line 6173 pos 15: 'child != null': is

我有点困惑我应该如何将价值传递给它。我见过一些类似的问题，但它们没有帮助。喜欢this 或这个question。这些都没有任何这些错误。你能告诉我我做错了什么吗？什么问题？请帮忙。

Answer 1

好吧，对于像我一样愚蠢并且遇到与我相同问题的人，这是解决问题的方法， 因此，我没有将正确的值传递给 Search 委托，也没有正确拾取它。这是代码的固定部分

   class DataSearch extends SearchDelegate {
      DataSearch({
        @required this.activeTab,
      });

  final activeTab;

@override
  Widget buildResults(BuildContext context) {
        if (activeTab == "subparticipants") {
...... .
....
..