我需要获取我的Firebase数据库的最后一个孩子 [英] i need to get Last child of my firebase databse

问题描述

我想从我的Firebase数据结构中获取最后一个孩子，在该数据结构中我只知道接收到的孩子的第一个孩子的引用

i want to get last child from my firebase data structure in which i only know the reference of received and first child of it

我尝试了这个，但是它将返回所有孩子，但是我只需要在查询limiTolast(1)中使用的最后一个孩子

i try this one but it will return all child but i need only last one that use in query limiTolast(1) like this

  DatabaseReference users = mDatabase.child("received");
      //  DatabaseReference receiver = users.child(firebaseUser.getUid());
        final DatabaseReference receiver = 
    users.child("GTjrWgpKjoeXUt4JdBJTYP1JkVT2");

        receiver.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {

                Log.d(TAG, "key count=" + postSnapshot.getKey());

                for (DataSnapshot sender: postSnapshot.getChildren()) {

                    Log.d(TAG, "sender key count=" + sender.getKey());

                }

            }


        }


        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.e("SHAN " ,databaseError.getMessage());
        }
    });

推荐答案

如果知道父节点(received/GTjrWgpKjoeXUt4JdBJTYP1JkVT2/fnBOM...)的完整路径，则只能使用limitToLast(1)获取该位置下的最后一个子节点:

If you know the complete path of the parent node (received/GTjrWgpKjoeXUt4JdBJTYP1JkVT2/fnBOM...), you can get only the last child node under that location with limitToLast(1):

DatabaseReference ref = users.child("GTjrWgpKjoeXUt4JdBJTYP1JkVT2/fnBOM...`");
ref.orderByKey().limitToLast(1).addChildEventListener(...

如果您不知道父节点的完整路径，则无法检索子节点的子集.

If you don't know the complete path to the parent node, there is no way to retrieve a subset of the child nodes.

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