在 flutter 中使用 Streambuilder 时出现时间戳错误

Question

使用 stream 构建器时出现错误，并且

看起来是由于数据类型不匹配，我试着自己找出来，但没能找到。

并且不知道到底是哪个语句导致了这个错误......

错误是

type 'Timestamp' is not a subtype of type 'DateTime?'

这是我的代码消息 model class

class MessageModel {
  String? messageid;
  String? sender;
  String? msg;
  bool? isseen;
  DateTime? createdon;

  MessageModel(
      {this.messageid, this.sender, this.createdon, this.isseen, this.msg});

  MessageModel.fromMap(Map<String, dynamic> map) {
    messageid = map['messageid'];
    sender = map['sender'];
    msg = map['msg'];
    isseen = map['isseen'];
    createdon = map['createdon'];
  }

  Map<String, dynamic> toMap() {
    return {
      'messageid': messageid,
      'sender': sender,
      'msg': msg,
      'isseen': isseen,
      'createdon': createdon,
    };
  }
}

这是我在其中获取记录的 Streambuilder 代码

StreamBuilder(
              stream: FirebaseFirestore.instance
                  .collection('chatrooms').doc(widget.chatroommodel.chatroomid).collection('messages')
                  .snapshots(),
              builder: (context, snapshot) {
                if (snapshot.connectionState == ConnectionState.active) {
                  print('i am active ');
                  if (snapshot.hasData) {
                    print('hasdata');
                    QuerySnapshot querysnapshot =
                    snapshot.data as QuerySnapshot;
                    if (querysnapshot.docs.length > 0) {
                      print('length greate than zero');
                      //
                      List<Map<String, dynamic>> maplist = [];
                      for (int x = 0; x < querysnapshot.docs.length; x++) {
                        Map<String, dynamic> messagemap = querysnapshot.docs[x]
                            .data() as Map<String, dynamic>;
                        maplist.add(messagemap);
                      }
                      print(maplist);

                      return Expanded(
                        child: ListView.builder(
                            itemCount: maplist.length,
                            itemBuilder: (context, index) {
                              MessageModel tempmsg =
                              MessageModel.fromMap(maplist[index]);
                              return ListTile(
                                onTap: ()  {

                                },
                                ,
                                title: Text(
                                  tempmsg.msg.toString(),
                                  style: TextStyle(fontSize: 20),
                                ),
                                subtitle: Text(tempmsg.createdon.toString()),
                              );
                            }),
                      );
                    } else {
                      return Text('Has Data but No user Found');
                    }
                  } else {
                    if (snapshot.hasError) {
                      return Text('error found');
                    } else {
                      return Text('empty..');
                    }
                  }
                } else {
                  return CircularProgressIndicator();
                }
              })

这是 function，我正在将数据设置为 Firestone

void sendmessage(String msg) async {
    MessageModel temp = MessageModel(
      messageid: uuid.v1(),
      msg: msg,
      sender: widget.usermodel.userid,
      isseen: false,
      createdon: DateTime.now(),
    );
//here special reason not giving await..wtch chatapp video no.8
    // if i place await..it will not allow to go further until msg deliver to server
    // note it that firebase store it to localdevice if net not available and deliver it on net availability
    //make some practise
     FirebaseFirestore.instance
        .collection('chatrooms')
        .doc(widget.chatroommodel.chatroomid).collection('messages').doc(temp.messageid)
        .set(temp.toMap());
     txtmsgcontroller.clear();
  }

Answer 1

它由来自 stackoverflow 的一些旧问题解决..

我只是错过了在消息 class model 中转换为日期

这是答案

MessageModel.fromMap(Map<String, dynamic> map) {
    print(map['createdon']);
    messageid = map['messageid'];
    sender = map['sender'];
    msg = map['msg'];
    isseen = map['isseen'];
    createdon = map['createdon'].toDate();
//i corrected this line and solved
  }