迭代嵌套的 Firebase 数据库节点时出现 DatabaseException

Question

我正在尝试迭代具有以下数据快照的嵌套 Firebase 数据库：

 DataSnapshot { key = Presidents, value = {1={aspirantName=Uh Ky, thumbnail=434, currentVotes=324595}, position=1, 2={aspirantName=Rao O, thumbnail=3, currentVotes=32}, numberofAspirants=3, docketName=Presidents} }

但是得到这个异常：

com.google.firebase.database.DatabaseException：无法将 java.lang.String 类型的对象转换为 com.example.esir.jualeader.Aspirant 类型

数据快照是来自

的日志

private void getAspirantsData(DataSnapshot dataSnapshot) {
    aspirantsArrayList.clear(){
    Log.e("Ds", "" + dataSnapshot); //Prints  DataSnapshot { key = Presidents, value = {1={aspirantName=Uh Ky, thumbnail=434, currentVotes=324595}, position=1, 2={aspirantName=Rao O, thumbnail=3, currentVotes=32}, numberofAspirants=3, docketName=Presidents} }
    Iterable<DataSnapshot>iterable=dataSnapshot.getChildren();
    Iterator<DataSnapshot>iterator=iterable.iterator();
    while (iterator.hasNext()){
Aspirant aspirant=iterator.next().getValue(Aspirant.class); // com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.esir.jualeader.Aspirant
        Log.e("Aspirant ", "" + aspirant.getAspirantName()+" "+aspirant.getCurrentVotes()+" "+aspirant.getThumbnail());//This Works therefore Aspirant Object has Been Created
        aspirantsArrayList.add(aspirant);
    }
}

任何人都可以就异常发生的原因提供帮助吗？它也尝试将哪个字符串转换为我的 Aspirant 对象。

这是我的应聘者课程

public class Aspirant {
    private String aspirantName;
    private int currentVotes;
    private int thumbnail;

    public Aspirant(){

    }
    public Aspirant(String aspirantName, int currentVotes, int thumbnail){
        this.aspirantName=aspirantName;
        this.currentVotes=currentVotes;
        this.thumbnail=thumbnail;
    }

    public String getAspirantName() {
        return aspirantName;
    }

    public void setAspirantName(String aspirantName) {
        this.aspirantName = aspirantName;
    }

    public int getCurrentVotes() {
        return currentVotes;
    }

    public void setCurrentVotes(int currentVotes) {
        this.currentVotes = currentVotes;
    }

    public int getThumbnail() {
        return thumbnail;
    }

    public void setThumbnail(int thumbnail) {
        this.thumbnail = thumbnail;
    }
}

以下是我的 Firebase 数据库结构

{
    "Presidents" : {
      "1" : {
        "aspirantName" : "Urhu atta",
        "currentVotes" : 324595,
        "thumbnail" : 434
      },
      "2" : {
        "aspirantName" : "Rla Oga",
        "currentVotes" : 32,
        "thumbnail" : 3
      },
      "docketName" : "Presidents",
      "numberofAspirants" : 3,
      "position" : 1
    },
    "Senetors" : {
      "docketName" : "Senetors",
      "numberofAspirants" : 5,
      "position" : 2
    }
}

Answer 1

您的 JSON 中有不兼容的数据。在President 下，您有两个有效的Aspirant 对象：

  "1" : {
    "aspirantName" : "Urhu atta",
    "currentVotes" : 324595,
    "thumbnail" : 434
  },

和

  "2" : {
    "aspirantName" : "Rla Oga",
    "currentVotes" : 32,
    "thumbnail" : 3
  },

但是你也有这些属性，没有一个可以转换成Aspirant：

  "docketName" : "Presidents",
  "numberofAspirants" : 3,
  "position" : 1

这是 Firebase 文档建议不要将不同类型的数据嵌套在一个公共根目录下的众多原因之一。更好的数据结构是：

"Dockets": {
    "Presidents" : {
      "docketName" : "Presidents",
      "numberofAspirants" : 3,
      "position" : 1
    },
    "Senetors" : {
      "docketName" : "Senetors",
      "numberofAspirants" : 5,
      "position" : 2
    }
},
"Candidates": {
    "Presidents" : {
      "1" : {
        "aspirantName" : "Urhu atta",
        "currentVotes" : 324595,
        "thumbnail" : 434
      },
      "2" : {
        "aspirantName" : "Rla Oga",
        "currentVotes" : 32,
        "thumbnail" : 3
      }
    },
    "Senetors" : {
      ... nothing here yet
    }
}

现在您可以从Candidates 键下安全地读取所有Aspirant 对象。

Answer 2

尝试用这个替换你的整个“getAspirantsData”函数：

private void getAspirantsData(DataSnapshot dataSnapshot) 
{
aspirantsArrayList.clear()
Log.e("Ds", "" + dataSnapshot);
for(DataSnapshot snap : datasnapshot.getChildren()
    aspirantsArrayList.add(snap.getValue(Aspirant.class);
}