从Firebase获取数据需要花费大量时间

Question

我正在使用Firebase来存储我的应用程序中的数据。我现在只有4个用户。而查询它们平均要花费35秒以上。可能是什么问题？这是由于firebase造成的还是我在某处未正确编写代码？是否有其他方法可以加快流程？我只是从数据库中读取特定用户的帖子，然后在recyclerView中显示。下面是我的代码。

Firebase数据库结构

Users: { 
            7828272892 : {
                 name: xyz, 
                 gender: male,
                 phoneNo: 7828272892
                 Posts: {
                     SomeKey1: {
                         content: "This is post 1", Var2: "kkk"} }},
            7924272894 : {name: abc, gender: male, phoneNo: 7924272894} 
        }

片段类的代码

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;


import java.util.ArrayList;
import java.util.List;

import static android.view.View.GONE;

public class MyWallFragment extends Fragment {
    private DatabaseReference databaseReference;
    private List<Post> allItems = new ArrayList<>();
    private ProgressBar pgsBar;
    private RecyclerViewAdapterMyWall rcAdapter;


    public MyWallFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        databaseReference = FirebaseDatabase.getInstance().getReference();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View rootView = inflater.inflate(R.layout.fragment_my_wall, container, false);

        final RecyclerView rView = rootView.findViewById(R.id.recycler_view);
        pgsBar = (ProgressBar)rootView.findViewById(R.id.pBar);

        rView.setLayoutManager(new LinearLayoutManager(getActivity()));
        rcAdapter = new RecyclerViewAdapterMyWall(allItems);
        rView.setAdapter(rcAdapter);
        rView.setItemAnimator(new DefaultItemAnimator());

        String myNumber = FirebaseAuth.getInstance().getCurrentUser().getPhoneNumber();
        String phnNo = myNumber;
        if (phnNo.length()>10) {
            phnNo = phnNo.substring(phnNo.length()-10);
        }

        databaseReference.child("Users").child(phnNo).child("Posts").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                allItems = new ArrayList<Post>();
                for (DataSnapshot postSnapshot: snapshot.getChildren()) {
                    String content = postSnapshot.child("content").getValue().toString();
                    Post post = new Post("x","Y", content);
                    allItems.add(post);
                    rcAdapter.addItem(post);
                }

                pgsBar.setVisibility(GONE);
            }

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

            }
        });

        return rootView;
    }

}