如何按照儿童在firebase中的键值进行排序？ [英] How to sort by children key value in firebase?

问题描述

这棵树看起来像这样：

someprojectId：{
 dateAdded：Firebase.TimeStamp 
}，
 
someProjectid2：{
 dateadded：Firebase.Timestamp 
} 
 
} 
  

我在android中调用它：

  mDatabase.child（projects）。orderByChild（dateAdded）。 addValueEventListener（new ValueEventListener（）{
  

然而，它并没有正确排序，事实上呢？

解决方案

这将有助于看到如何实际处理 onDataChange code>。但是我的猜测是你无法循环使用子元素：



  mDatabase 
 .child（projects）
 .orderByChild（dateAdded）
 .addValueEventListener（new ValueEventListener（）{
 public （DataSnapshot child：snapshot.getChildren（））{
 System.out.println（child.getKey（））; void onDataChange（DataSnapshot snapshot）{
 
 
 
 ... 
  




I am trying to sort projects based on the dateAdded:

The tree looks like this:

projects: {
    "someprojectId": {
       dateAdded: Firebase.TimeStamp
    },

    "someProjectid2":{
      dateAdded: Firebase.Timestamp
   }

}

I am calling it like so in android:

mDatabase.child("projects").orderByChild("dateAdded").addValueEventListener(new ValueEventListener() {

However, it is not sorting it correctly, or at all for that matter of fact?

解决方案

It would help to see how you actually handle the data in onDataChange. But my guess is that you're failing to loop over the children:

mDatabase
  .child("projects")
  .orderByChild("dateAdded")
  .addValueEventListener(new ValueEventListener() {
    public void onDataChange(DataSnapshot snapshot) {
      for (DataSnapshot child: snapshot.getChildren()) {
        System.out.println(child.getKey());
      }
    }
    ...

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