Flutter：我有两个函数可以在我的 Flutter 应用程序中读取 Firebase 数据.现在我想在一个文本小部件中总结两个函数返回值

我想在我的Flatter应用程序中对两个不同的firebase集合字段值求和.这就是我编写两个函数的原因.我可以对一个集合字段值求和，但单个文本小部件中的两个集合字段值求和不起作用，或者我不知道如何执行此操作..

Scaffold(
  body: SafeArea(
      child: Container(
    child: StreamBuilder<double?>(
      stream: getFundData(),
      builder: (context, snapshort) {
        if (snapshort.connectionState == ConnectionState.waiting) {
          return Center(child: CircularProgressIndicator());
        }
        if (snapshort.hasData) {
          double data = snapshort.data!;
          return Center(child: Column(
            children: [
              Text("$data"),
              
            ],
          ));
        }

        return Text("data");
      },
    ),
  )),
);

功能代码

Stream<double> getFundData() async* {
  final result =
  await FirebaseFirestore.instance.collection('Use-of-fund').get();
  double totalFundAmount = 0;
  for (var doc in result.docs) {
    totalFundAmount += doc['Amount'];
  }
  yield totalFundAmount;
}

Stream<double> getUserBalanceData() async* {
  final result = await FirebaseFirestore.instance.collection('User-data').get();
  double userTotalAmount = 0;
  for (var doc in result.docs) {
    userTotalAmount += doc['Balance'];
  }
  yield userTotalAmount;
}

现在我想求和userTotalAmount和totalFundAmount