Flutter/Firestore：“QuerySnapshot”类没有实例获取器“document”

Question

我有一个应用程序，我想从 Firestore 数据库中检索数据，这些数据是 uid 文档中表示的消息，如此处所述，这些消息存储如下： ChatRoom->chatRoomId->chat-> uid-> 消息

但我收到此错误：

在构建 StreamBuilder(dirty, state: _StreamBuilderBaseState#56cb5): 类 'QuerySnapshot' 没有实例 吸气剂'文档'。接收方：“QuerySnapshot”实例已尝试 调用：文档

相关的导致错误的小部件是：StreamBuilder file:///Users/ahmedhussain/Downloads/khamsat/Client%20Apps/HPX-KSA/hpx_ksa/lib/Screens/messages.dart:21:12 抛出异常时，这是堆栈： #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5) #1 _MessagesState.chatRoomList。 （包：hpxksa/Screens/messages.dart:25:38）

这是我的代码：

class _MessagesState extends State<Messages> {
  
  Stream chatRoomsStream;

  Widget chatRoomList(){
    return StreamBuilder(
      stream: chatRoomsStream,
      builder: (context, snapshot){
        return snapshot.hasData ? ListView.builder(
            itemCount: snapshot.data.document.length,
            itemBuilder: (context, index){
              return ChatRoomTile(
                 username: snapshot.data.documents[index].data["chatRoomId"]
                      .toString().replaceAll("_", "").replaceAll(Constants.myName, "replace"),
                  chatRoomId:snapshot.data.documents[index].data["chatRoomId"]
              );
            }) : Container();
      }
      );
  }

  getUserInfogetChats() {
    DatabaseService().getChatRooms(Constants.myName).then((value) {
      setState(() {
        chatRoomsStream = value;
      });
    });
  }

  @override
  void initState() {
    getUserInfogetChats();
    super.initState();
  }


@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: chatRoomList(),
    );
  }
}


class ChatRoomTile extends StatelessWidget {
  final String username;
  final String chatRoomId;
  ChatRoomTile({this.username, this.chatRoomId});

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: (){
        Navigator.push(context, MaterialPageRoute(builder: (context)=>Conversation(chatRoomId: chatRoomId,)));
      },
      child: Container(
        color: Colors.black26,
        padding: EdgeInsets.symmetric(horizontal: 24, vertical: 16),
        child: Row(
          children: <Widget>[
            Container(
              height: 40,
              width: 40,
              alignment: Alignment.center,
              decoration: BoxDecoration(
                color: kPrimaryColor,
                borderRadius: BorderRadius.circular(40),
              ),
              child: Text("${username.substring(0,1).toUpperCase()}"),
            ),
            SizedBox(width: 8,),
            Text(username),
          ],
        ),
      ),
    );
  }
}

这是我获取包含用户名的聊天记录的函数：

 getChatRooms(String username)async{
    return await Firestore.instance.collection("ChatRoom").
    where("users", arrayContains: username).
    snapshots();

  }

Answer 1

您收到的错误非常清楚问题是什么。 QuerySnapshot 没有 document 属性。您可能打算使用documents 属性，这与您尝试使用ListView 更加一致。

将snapshot.data.document 的实例更改为snapshot.data.documents 将解决此特定问题。

Answer 2

  return StreamBuilder(
      stream: chatRoomStream,
      builder: (context, snapshot) {
        return snapshot.hasData
            ? ListView.builder(
                itemCount: snapshot.data.docs.length,
                itemBuilder: (context, index) {
                  return ChatRoomTile(
                      **snapshot.data.docs[index].data()['chatRoomId']**);
                },
              )
            : Container();
      },
    );