Firebase Realtime Database在Unity3D中查询结果多出额外元素如何解决

问题描述 #

在Unity3D中调用Firebase Realtime Database接口读取数据时，偶发出现DataSnapshot返回结果异常：查询得到的子项中多出了由数据库最后一条元素拆分出的额外字段。

运行环境 #

• Unity3D版本：2019.2.18f1
• Firebase版本：8.6.1

数据库结构 #

desks节点的存储数据如下：

"desks": {
    "0" : {
      "deskID" : 0,
      "deskName" : "Sol iç 1"
    },
    "1" : {
      "deskID" : 1,
      "deskName" : "Sol iç 2"
    },
    "2" : {
      "deskID" : 2,
      "deskName" : "Sol iç 3"
    },
    "3" : {
      "deskID" : 3,
      "deskName" : "Sağ iç 1"
    },
    "4" : {
      "deskID" : 4,
      "deskName" : "Sağ iç 2"
    },
    "5" : {
      "deskID" : 5,
      "deskName" : "Sağ iç 3"
    },
    "6" : {
      "deskID" : 6,
      "deskName" : "Sol dış 1"
    },
    "7" : {
      "deskID" : 7,
      "deskName" : "Sol dış 2"
    },
    "8" : {
      "deskID" : 8,
      "deskName" : "Sağ dış 1"
    },
    "9" : {
      "deskID" : 9,
      "deskName" : "Sağ dış 2"
    },
    "10" : {
      "deskID" : 10,
      "deskName" : "Sağ dış 3"
    },
    "11" : {
      "deskID" : 11,
      "deskName" : "Sağ dış 4"
    },
    "12" : {
      "deskID" : 12,
      "deskName" : "Sağ dış 5"
    },
    "13" : {
      "deskID" : 13,
      "deskName" : "Sağ dış 6"
    },
    "9999" : {
      "deskID" : 9999,
      "deskName" : "Personel"
    }
}

相关代码 #

数据查询代码 #

FirebaseDatabase.DefaultInstance.GetReference("desks").GetValueAsync().ContinueWithOnMainThread((task) =>
{
    Desks desks = new Desks();
    if (task.IsFaulted)
    {
        Debug.Log("error read desk data");
    }
    else if (task.IsCompleted)
    {
        DataSnapshot snapshot = task.Result;

        Debug.Log(snapshot.ChildrenCount);
        if (snapshot.ChildrenCount > 0)
        {
            foreach (DataSnapshot snapshotChild in snapshot.Children)
            {
                try
                {
                    Desk desk = JsonUtility.FromJson<Desk>(snapshotChild.GetRawJsonValue());
                    Debug.Log(desk.deskName);
                    desks.desks.Add(desk);

                }catch(Exception ex)
                {
                    Debug.Log(snapshotChild.Key);
                    Debug.Log(snapshotChild.Value);
                    Debug.Log(ex.Data);
                    Debug.Log(ex.Message);
                }
            }
        }
    }
});

Desk实体类定义 #

[Serializable]
public class Desk
{
    public int deskID;
    public string deskName;
}

异常表现 #

预期desks节点应返回15个子节点，但是偶发返回17个子节点：第16个子节点Key为deskID、值为9999，第17个子节点Key为deskName、值为Personel，正好是原本Key为9999的子节点的两个字段被拆分当成了独立子节点返回。

修复结果 #

该问题参考Firebase官方维护者Frank van Puffelen的解答后已修复，连续测试30次均能正常获取到正确数据。 #

内容的提问来源于stack exchange，提问作者Emre Metilli