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为什么Another exception was thrown: FormatException: Invalid number (at character 1)在一切恢复正常之前，我的屏幕上会出现错误几微秒。有时它甚至不会发生。下面是我的 StreamBuilder 函数：

_delivered() {
    print('In the delivered function:${resId},${customerId}, ');
    return StreamBuilder<QuerySnapshot>(
        stream: Firestore.instance
            .collection('restaurants')
            .document(resId)
            .collection('customers')
            .document(customer)
            .collection('orders')
            .where('deliveryTime', isGreaterThan: '')
            .snapshots(),
        builder: (context, snapshot) {
          print('Does snapshop have data? ${snapshot.hasData}');
          if (!snapshot.hasData) return Container();

          List deliveredListFromServer = snapshot.data.documents;
          return Expanded(
            child: ListView(
              shrinkWrap: true,
              children: deliveredListFromServer.map((item) {
                print('document id: ${item.documentID}');
                return InkWell(
                  child: SizedBox(
                    height: 50,
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: <Widget>[
                        SizedBox(
                          width: 80,
                          child: Text( …