扑向溪流构造者陷入了状态，等待重新宣扬回到页面

Question

我是Flutter的新手，我对StreamBuilder有问题。启动时，返回了来自Firestore的快照，但是当我导航到另一个页面时，然后返回页面时，快照的连接状态被卡在等待中。当热重新加载或刷新页面时，显示数据并正常工作。该问题仅在重新散布回页面时才发生。我认为，由于它不会添加新数据或编辑数据，因此StreamBuilder不会更新且不会重建。

初始streambuilder

重新恢复后

我还使用dataTable在表格中显示我的数据，以下代码可能会有点长。

return StreamBuilder<QuerySnapshot>(
    stream: providerDBsnaps,
    builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
      switch (snapshot.connectionState) {
        case ConnectionState.none:
          return const Text('Something went wrong');
        case ConnectionState.waiting:
          return const LinearProgressIndicator();
        case ConnectionState.active:
          if (snapshot.hasData) {
            final List<DocumentSnapshot> documents = snapshot.data!.docs;

            providers = documents
                .map((e) =>
                    ProviderList.fromMap(e.data() as Map<String, dynamic>))
                .toList();

            List<DataRow> providerListItems() {
              List<DataRow> providerList = [];
              for (var i = 0; i < providers.length; i++) {
                bool status = providers[i].status;
                DataRow dataRow =
                    DataRow(onSelectChanged: (bool? newVal) {}, cells: [
                  DataCell(Container(
                    width: 30,
                    child: Text((i + 1).toString()),
                  )),
                  DataCell(Container(
                    width: 120,
                    child: Text(providers[i].name),
                  )),
                  DataCell(Container(
                    width: 200,
                    child: Text(providers[i].address),
                  )),
                  DataCell(
                    Container(
                        width: 120, child: Text(providers[i].contact)),
                  ),
                  DataCell(
                    Container(width: 100, child: Text(providers[i].phone)),
                  ),
                  DataCell(
                    MouseRegion(
                      cursor: SystemMouseCursors.click,
                      child: Container(
                        alignment: Alignment.center,
                        width: 42,
                        height: 22,
                        child: FlutterSwitch(
                          value: providers[i].status,
                          width: 40.0,
                          height: 20.0,
                          borderRadius: 30.0,
                          onToggle: (val) {
                            setState(() {
                              showDialog(
                                  context: context,
                                  builder: (context) => AlertDialog(
                                        title: const CustomText(
                                          text: "Warning",
                                          weight: FontWeight.bold,
                                          size: 22,
                                        ),
                                        content: const CustomText(
                                          text:
                                              "Are you sure you want to change the status?",
                                          size: 16,
                                        ),
                                        actions: [
                                          TextButton(
                                            onPressed: () {
                                              status = val;
                                              providerDB
                                                  .doc(providers[i].id)
                                                  .update(
                                                      {'p_status': status});
                                              Navigator.pop(context);
                                            },
                                            child: const CustomText(
                                                text: 'Yes'),
                                          ),
                                          TextButton(
                                            onPressed: () {
                                              Navigator.pop(context);
                                            },
                                            child: const CustomText(
                                                text: 'No'),
                                          )
                                        ],
                                      ));
                            });
                          },
                        ),
                      ),
                    ),
                  ),
                  DataCell(Row(
                    children: [
                      SizedBox(
                        width: 30,
                        child: MaterialButton(
                          padding: const EdgeInsets.all(7.0),
                          onPressed: () {
                            menuController
                                .changeActiveitemTo(EditingPageName);
                            Navigator.push(
                              context,
                              MaterialPageRoute(
                                builder: (context) => ProviderEditPage(
                                    existing: providers[i]),
                              ),
                            );
                          },
                          child: const Icon(
                            Icons.edit,
                            color: Colors.black,
                            size: 18,
                          ),
                        ),
                      ),
                      const SizedBox(
                        width: 5,
                      ),
                      SizedBox(
                        width: 30,
                        child: MaterialButton(
                          padding: const EdgeInsets.all(7.0),
                          onPressed: () {
                            showDialog(
                                context: context,
                                builder: (context) => AlertDialog(
                                      title: const CustomText(
                                        text: "Delete Notice",
                                        weight: FontWeight.bold,
                                        size: 22,
                                      ),
                                      content: const CustomText(
                                        text:
                                            "Are you sure you want to delete the item?",
                                        size: 16,
                                      ),
                                      actions: [
                                        TextButton(
                                          onPressed: () {
                                            providerDB
                                                .doc(providers[i]
                                                    .id
                                                    .toString())
                                                .delete();
                                            Navigator.pop(context);
                                          },
                                          child:
                                              const CustomText(text: 'Yes'),
                                        ),
                                        TextButton(
                                          onPressed: () {
                                            Navigator.pop(context);
                                          },
                                          child:
                                              const CustomText(text: 'No'),
                                        )
                                      ],
                                    ));
                          },
                          child: const Icon(
                            Icons.delete,
                            color: Colors.black,
                            size: 18,
                          ),
                        ),
                      ),
                    ],
                  ))
                ]);
                providerList.add(dataRow);
              }
              return providerList;
            }

            return Container(
              height: 550,
              padding: const EdgeInsets.all(16),
              margin: const EdgeInsets.only(bottom: 30),
              decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.circular(8),
                  boxShadow: [
                    BoxShadow(
                        offset: const Offset(0, 6),
                        color: lightGrey.withOpacity(.1),
                        blurRadius: 12),
                  ],
                  border: Border.all(color: lightGrey, width: .5)),
              child: DataTable(
                columnSpacing: 0,
                showCheckboxColumn: false,
                columns: const [
                  DataColumn(
                    label: CustomText(
                      text: "No.",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Name",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Address",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Contact Person",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Phone Number",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Status",
                      weight: FontWeight.bold,
                    ),
                  ),
                  DataColumn(
                    label: CustomText(
                      text: "Tools",
                      weight: FontWeight.bold,
                    ),
                  ),
                ],
                rows: providerListItems(),
              ),
            );
          } else {
            return const Text('No data...');
          }
        case ConnectionState.done:
          return const Text('Something went wrong');
        default:
          return const Text('Something went wrong');
      }
    });

}

我做错了什么？还是一个错误？问题是否像我认为数据没有更新，因此流构建器仅构建一次？如果是这样，您可以为我提供解决方案，我似乎找不到解决方案...谢谢！

- ＆gt;编辑

ProviderDbsnaps的初始化

@override
void initState() {
  super.initState();
  providerDBsnaps = providerDB.snapshots();
  providerDBsnaps.listen((snapshot) {
  if (snapshot.docs.isNotEmpty) {
    final List<DocumentSnapshot> documents = snapshot.docs;

    providers = documents
        .map((e) => ProviderList.fromMap(e.data() as Map<String, dynamic>))
        .toList();
  }
});
}

Answer 1

连接状态将保留在“等待”中，直到发送新快照为止。

解决它的一种方法是将您的流构建器放入状态fullwidget中，以便保持“提供者”的状态。

在您的州类中，函数“ ProviderListItems”可以在流构建器之外。

然后，您的FutureBuilder可能会像：

builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
  switch (snapshot.connectionState) {
    case ConnectionState.none:
    case ConnectionState.done:
      return const Text('Something went wrong');
    case ConnectionState.active:
      if (snapshot.hasData) {
        final List<DocumentSnapshot> documents = snapshot.data!.docs;
        providers = documents
            .map((e) =>
                ProviderList.fromMap(e.data() as Map<String, dynamic>))
            .toList();
      } else {
        providers = [];
      }
      break;
    default:
      break;
  }
  if(providers.isNotEmpty) {
    return Container(
      ...
      );
  } else {
    return const Text('No data...');
  }

我认为更容易的另一种方式是在发送事件时聆听您在Initstate内部的流并更新提供商。

class _MyWidget extends State<MyWidget> {
  List providers = [];

  @override
  void initState() {
    providerDBsnaps.listen((snapshot) {
      if (snapshot.hasData) {
        final List<DocumentSnapshot> documents = snapshot.data!.docs;
        providers = documents
                .map((e) =>
                    ProviderList.fromMap(e.data() as Map<String, dynamic>))
                .toList();
       } else {
            providers = [];
       }
       setState((){});
    };
  }
  
  @override
  Widget build(BuildContext context) {
      if(providers.isNotEmpty) {
        return Container(
          ...
          );
      } else {
        return const Text('No data...');
      }
  }

  List<DataRow> providerListItems() {
    final List<DataRow> providerList = [];
    ...
    return providerList;
  }