android - NoSuchMethodError：在 null 上调用了 getter 'idCommande'

Question

我想列出数据库中“Commande”表中的数据时遇到问题，我不知道问题出在哪里，通常 idCommande 在数据库中是自动递增的，但在这里它仍然显示为空，有人可以吗帮帮我，这是我为了列出订单而实现的代码，我评论了给我错误的行

StreamBuilder<List<CommandeWithClient>> _buildCommandeList(
      BuildContext context) {
    final dao = Provider.of<CommandeDao>(context);
    return StreamBuilder(
      stream: showCompleted ? dao.watchCompletedCommandes() : dao
          .watchAllCommandes(),
      builder: (context, AsyncSnapshot<List<CommandeWithClient>> snapshot) {
        final commandes = snapshot.data ?? List();
        return ListView.builder(
          scrollDirection: Axis.vertical,
          shrinkWrap: true,
          itemCount: commandes.length,
          itemBuilder: (_, index) {
            final itemCommande = commandes[index];
            return _buildListItem(itemCommande, dao);//the line that gives me the error
          },
        );
      },
    );
  }

  Widget _buildListItem(CommandeWithClient itemCommande, CommandeDao dao) {
    return Slidable(
      actionPane: SlidableDrawerActionPane(),
      secondaryActions: <Widget>[
        new IconSlideAction(
          caption: 'Delete',
          color: Colors.red,
          icon: Icons.delete,
          onTap: () => dao.deleteCommande(itemCommande.commande),
        )

      ],
      child: CheckboxListTile(
        title: Text(itemCommande.commande.idCommande.toString()), //here too
        value: itemCommande.commande.completed,
        onChanged: (newValue) {
          dao.updateCommande(
              itemCommande.commande.copyWith(completed: newValue));
        },
      ),
    );
  }

这是错误：

/flutter (21715): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (21715): The following NoSuchMethodError was thrown building:
I/flutter (21715): The getter 'idCommande' was called on null.
I/flutter (21715): Receiver: null
I/flutter (21715): Tried calling: idCommande
I/flutter (21715): 
I/flutter (21715): When the exception was thrown, this was the stack:
I/flutter (21715): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
I/flutter (21715): #1      HomePage._buildListItem (package:inwi_app/HomePage.dart:617:43)
I/flutter (21715): #2      HomePage._buildCommandeList.<anonymous closure>.<anonymous closure> (package:inwi_app/HomePage.dart:597:20)
I/flutter (21715): #3      SliverChildBuilderDelegate.build (package:flutter/src/widgets/sliver.dart:442:15)
I/flutter (21715): #4      SliverMultiBoxAdaptorElement._build.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1153:67)
I/flutter (21715): #5      _HashMap.putIfAbsent (dart:collection-patch/collection_patch.dart:137:29)
I/flutter (21715): #6      SliverMultiBoxAdaptorElement._build (package:flutter/src/widgets/sliver.dart:1153:26)
I/flutter (21715): #7      SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1166:55)
I/flutter (21715): #8      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2320:19)
I/flutter (21715): #9      SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:1159:11)
I/flutter (21715): #10     RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:354:23)
I/flutter (21715): #11     RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:1715:58)
I/flutter (21715): #12     PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:796:15)
I/flutter (21715): #13     RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:1715:13)
I/flutter (21715): #14     RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:343:5)
I/flutter (21715): #15     RenderSliverMultiBoxAdaptor.addInitialChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:427:5)
I/flutter (21715): #16     RenderSliverList.performLayout (package:flutter/src/rendering/sliver_list.dart:78:12)
I/flutter (21715): #17     RenderObject.layout (package:flutter/src/rendering/object.dart:1619:7)
I/flutter (21715): #18     RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:181:11)
I/flutter (21715): #19     RenderObject.layout (package:flutter/src/rendering/object.dart:1619:7)
I/flutter (21715): #20     RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:406:13)
I/flutter (21715): #21     RenderShrinkWrappingViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1663:12)
I/flutter (21715): #22     RenderShrinkWrappingViewport.performLayout (package:flutter/src/rendering/viewport.dart:1626:20)
I/flutter (21715): #23     RenderObject.layout (package:flutter/src/rendering/object.dart:1619:7)

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