使用推送创建的节点更新Firebase数据库 [英] Updating Firebase Database with nodes created with push

问题描述

我试图更新我的Firebase数据库中的值。这是数据库的结构：

如果 r_id ，我需要更新 status 的值到accepted c $ c>和 s_id 具有特定的值。这里的问题是每个 friend_data 子项的关键字都是使用push来生成的，像这样

 。 db.child（ friend_data）推（）的setValue（朋友）; 
  

我曾尝试和，但都不符合我的要求。我怎么去解决这个问题？

编辑：现在我明白我应该使用 Query 在这里。这是我试过的：

$ p $ final DatabaseReference db = FirebaseDatabase.getInstance（）。getReference（friend_data）;

Query query = db.orderByChild（r_id）。equalTo（f_id）.orderByChild（s_id）。equalTo（id）;
query.addListenerForSingleValueEvent（new DataEventListener（）{
@Override
public void onDataChange（DataSnapshot dataSnapshot）{
for（DataSnapshot child：dataSnapshot.getChildren（））{
。db.child（child.getKey（））。child（status）。setValue（accepted）;
}
}

@Override
public void onCancelled（DatabaseError databaseError）{


}）;


这不起作用，或者是因为出现此错误

java.lang.IllegalArgumentException：您不能合并多个orderBy调用！

所以，如何组合两个查询？

解决方案

我用 orderByChild 方法添加了一个Query，以便在服务器端自己过滤掉一大块数据（感谢这个 child 数据类型<$ c的其余数据$ c> DataSnapshot 具有我需要的所有必要信息。这里是查询

  Query query = db.orderByChild（r_id）。equalTo（f_id）; 
 query.addListenerForSingleValueEvent（new DataEventListener（）{
 @Override 
 public void onDataChange（DataSnapshot dataSnapshot）{
 for（DataSnapshot child：dataSnapshot.getChildren（））{
字符串child_s_id =（String）child.child（s_id）。getValue（）; 
字符串child_status =（String）child.child（status）。getValue（）; 
 $ b $如果（child_s_id.equals（id））{
 Log.e（Got value，f_id + -  x  - + id ++ child_status）; 
 
} 
} 
} 
 
 @Override 
 public void onCancelled（DatabaseError databaseError）{
 
 
}）; 
  

但是我再也达不到我的要求，因为我实际上需要修改其中的一个值 child 我不能使用像 setValue 这样的方法来改变 child < code $。



再次，我花了很长时间（这是一个白痴）弄清楚，我必须转换子（数据类型 DataSnapShot ）引用到 setValue 的引用上。它的工作原理

  child.getRef（）。child（status）。setValue（accepted）; 
  

这里是完整的代码。希望它帮助沿途的人



  Query query = db.orderByChild（r_id）。equalTo（f_id）; 
 query.addListenerForSingleValueEvent（new DataEventListener（）{
 @Override 
 public void onDataChange（DataSnapshot dataSnapshot）{
 for（DataSnapshot child：dataSnapshot.getChildren（））{
字符串child_s_id =（String）child.child（s_id）。getValue（）; 
字符串child_status =（String）child.child（status）。getValue（）; 
 
 if（child_s_id.equals（id））
 child.getRef（）。child（status）。setValue（accepted）; 
} 
} 
 
 @Override 
 public void onCancelled（DatabaseError databaseError）{
 $ b} 
}）; 
  




I am trying to update a value in my Firebase database. This is the structure of the database:

I need to update the value of status to "accepted" if the r_id and s_id have a specific value. The problem here is that the key for each friend_data child is generated using "push" like this

db.child("friend_data").push().setValue(friend);

I have tried this question here and this one here but both don't meet my requirements. How do I go about solving this one?

Edit: I understand now that I am supposed to use a Query here. This is what I tried:

final DatabaseReference db = FirebaseDatabase.getInstance().getReference("friend_data");

Query query = db.orderByChild("r_id").equalTo(f_id).orderByChild("s_id").equalTo(id);
query.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot child : dataSnapshot.getChildren()) {
            db.child(child.getKey()).child("status").setValue("accepted");
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

This does not work either because this error is raised

java.lang.IllegalArgumentException: You can't combine multiple orderBy calls!.

So how do I combine two Queries?

解决方案

I have finally got this to work after days of trying to figure it out.

I added a Query with orderByChild method to filter out a big chunk of data at the server side itself (thanks to this answer for the idea.) The remaining data which I got as child of data type DataSnapshot had all the necessary information that I needed. Here is the query

Query query = db.orderByChild("r_id").equalTo(f_id);
query.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot child : dataSnapshot.getChildren()) {
            String child_s_id = (String) child.child("s_id").getValue();
            String child_status = (String) child.child("status").getValue();

            if (child_s_id.equals(id)) {
                Log.e("Got value", f_id + " - x -" + id + " " + child_status);

            }
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

But again I could not meet my requirements, because I actually needed to modify one of the value in the child and I could not use any methods like setValue to change the value of child.

Again, it took me a long while (what an idiot) to figure out that I had to convert the child (of data type DataSnapShot) to a reference for setValue to work. And it worked

child.getRef().child("status").setValue("accepted");

Here is the completed code. Hope it helps someone along the way

Query query = db.orderByChild("r_id").equalTo(f_id);
query.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot child : dataSnapshot.getChildren()) {
            String child_s_id = (String) child.child("s_id").getValue();
            String child_status = (String) child.child("status").getValue();

            if (child_s_id.equals(id))
                child.getRef().child("status").setValue("accepted");
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

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