如何从Firebase中的ID列表中读取? [英] How to read from an ID list in Firebase?

问题描述

我有一个ID列表()，我想根据列表中的每个ID查询数据.我正在使用两个FutureBuilder:第一个用于获取ID列表，第二个用于显示与每个ID相关的数据.

I have a list of IDs (Future<List<String>> _listaIdEmpresasF) and I would like to query data based on each ID in the list. I'm using two FutureBuilders: The first one to get the list of IDs, and the second one to display the data related of each ID.

我的代码看起来像这样...

My code looks like this...

  @override
  void initState() {
    super.initState();
    _listaIdEmpresasF = _usuarioBloc.cargarEmpresasDeUsuario(_prefs.idUsuario);
  }

---

  Widget _crearListado(BuildContext context) {


  return FutureBuilder(
    future: _listaIdEmpresasF, 
    builder: (BuildContext context, AsyncSnapshot snapshot) {
        print(snapshot.connectionState);
        if (snapshot.connectionState == ConnectionState.done && snapshot.hasData != null){ 
          final List<String> _listaIdEmpresas = snapshot.data;

          return FutureBuilder(
            future: _empresaDatosBloc.cargarEmpresaDatosListado(_listaIdEmpresas),
            builder: (BuildContext context, AsyncSnapshot snapshot2) {
              print(snapshot2.connectionState);
              if (snapshot2.connectionState == ConnectionState.done && snapshot2.hasdata) {
                final List<EmpresaDatosModel> _listaEmpresas = snapshot2.data;
                return Stack(
                  children: <Widget>[
                    ListView.builder(
                      itemCount: _listaEmpresas.length,
                      itemBuilder: (context, i) {
                          return _crearItem(context, _listaEmpresas[i], i);
                      },

                      padding: EdgeInsets.only(left: 10.0, right: 10.0, top: 0.0, bottom: 20.0),
                    ),
                  ],
                ); 
              } else return Align(
                alignment: Alignment.center,
                child: Center (child: Image(image: AssetImage('Preloader.gif'), height: 500.0,)),
              );
            },
          );
        } 
        else return Align(
          alignment: Alignment.center,
          child: Center (child: Image(image: AssetImage('Preloader.gif'), height: 500.0,)),
        );
    },
  );
}

要从每个ID获取数据，我正在使用如下循环:

To get the data from each ID, I'm using a loop as follows:

Future<List<EmpresaDatosModel>> cargarEmpresaDatosListado(List<String> listaIdEmpresas) async {

    final List<EmpresaDatosModel> listaEmpresas = new List(); 

    listaIdEmpresas.forEach((id) async {
      Query resp = db.child('empresas/$id/datos');

      final snapshot = await resp.once();

      if (snapshot.value == null) return [];

      final temp = EmpresaDatosModel.fromJson(Map<String,dynamic>.from(snapshot.value));
      temp.idEmpresa = id;
      listaEmpresas.add(temp);
      print('${temp.nombre} subida');

      await resp.once().then((snapshot) {
        print("Los Datos de una Empresa se cargaron totalmente - ${temp.nombre}");
      });
    });
    listaEmpresas.forEach((element) {print('Emp ${element.nombre}');});
    return listaEmpresas; 
}

问题:我无法获取完整数据.例如，如果我在_listaIdEmpresas中具有三个ID，则该应用有时会显示一个公司(与第一个ID相关)的列表，有时会显示两个公司(第一个和第二个ID)，有时还会显示三个公司的列表.我认为这是因为第二个快照的ConnectionState在读取所有三个循环之前完成的.

The problem: I can't be able to obtain the full data. For example, if I have three IDs in _listaIdEmpresas, sometimes the app displays a list of one company (related to the first ID), sometimes two companies (first and secod ID) and sometimes the three companies. I supposed this is because the ConnectionState of the second snapshot is done before reading all three loops..

我试图添加一个条件，但是没有用...

I tried to add a condition but it didn't work...

      if (snapshot2.connectionState == ConnectionState.done && snapshot2.data.length == _listaIdEmpresas.length)

由于我配置的查询安全规则，我无法查询所有公司并将其过滤为公司列表.

I cannot query all companies and filter it as a list of companies due to query security rules that I configured.

我想在查询参数中包含ID的特定列表，但我不知道是否可能.

I would like to include the specific list of IDs in the query parameters, but I don't know if it's possible.

如何正确地从ID列表中读取数据?

How is the right way to read data from a list of IDs?

推荐答案

snapshot.key将为您提供该商品的ID

snapshot.key will give you the id of the item

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