count the nodes of a child in the firebase

问题

I have a structure like this in firebase:

Inside the node 'postagens-curtidas', I need to count this childrens and save this value at the 'qtdCurtidas' node, as the photo shows.

Is there a way to make this?

回答1:

final long count;
DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
ref.child("postagens-curtidas").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            count = dataSnapshot.getChildrenCount();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

This is how you get the total number of children nodes.

Assuming you have the key where qtdCurtidas is saved. You can save it as follows

ref.child("postagens-curtidas").child("Your Key Here").child("qtdCurtidas").setValue(count);

来源：https://stackoverflow.com/questions/53062882/count-the-nodes-of-a-child-in-the-firebase