我已经解决🙂了这个逻辑对我有用

final data = ChatStorage(
  roomId: widget.room!.id,
  chat: state.messages,
);

if (chatBox.isEmpty)
      chatBox.put(widget.room!.id, data);
    else {
      List<int>? roomIds = [];
      bool available = false;
      for (var chat in chatBox.values) {
        roomIds.add(chat.roomId!);
      }
      if (!roomIds.contains(widget.room!.id)) available = true;

      if (available) chatBox.put(widget.room!.id, data);
   }
}

我认为如果有人面临这样的问题，这种方法会有所帮助🙂