使用未指定的索引

Question

您好 StackOverflow 社区，我编写了一个代码来搜索 Firebase 数据库中的用户，但每次我尝试启动该代码时，它都不会向我显示用户。

在我的运行日志中，我收到以下消息：

W/PersistentConnection: pc_0 - 使用未指定的索引。您的数据将在客户端下载和过滤。考虑将 '".indexOn": "username"' at users 添加到您的安全和 Firebase 数据库规则中以获得更好的性能

这是我写的代码：

package com.example.ts.tsp.Fragment;


import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;

import com.example.ts.tsp.Adapter.UserAdapter;
import com.example.ts.tsp.Model1.User;
import com.example.ts.tsp.R;
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.Query;
import com.google.firebase.database.ValueEventListener;

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


public class SearchFragment extends Fragment {

    private RecyclerView recyclerView;
    private UserAdapter userAdapter;
    private List<User> mUsers;

    EditText search_bar;

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

        recyclerView = view.findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

        search_bar = view.findViewById(R.id.search_bar);

        mUsers = new ArrayList<>();
        userAdapter = new UserAdapter(getContext(), mUsers);
        recyclerView.setAdapter(userAdapter);

        readUsers();
        search_bar.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                searchUsers(s.toString().toLowerCase());

            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });
        return view;

    }

    private void searchUsers(String s){
        Query query = FirebaseDatabase.getInstance().getReference("Users").orderByChild("username")
                .startAt(s)
                .endAt(s+"\uf8ff");


        query.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                mUsers.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    User user = snapshot.getValue(User.class);
                    mUsers.add(user);
                }

                userAdapter.notifyDataSetChanged();
            }

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

            }
        });
    }

    private void readUsers(){

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("User");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (search_bar.getText().toString().equals("")){
                    mUsers.clear();
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                        User user = snapshot.getValue(User.class);
                        mUsers.add(user);
                    }

                    userAdapter.notifyDataSetChanged();
                }
            }

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

            }
        });
    }
}

还有其他班级：

package com.example.ts.tsp.Adapter;


import android.content.Context;
import android.content.SharedPreferences;
import android.support.annotation.NonNull;
import android.support.v4.app.FragmentActivity;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.example.ts.tsp.Fragment.ProfileFragment;
import com.example.ts.tsp.Model1.User;
import com.example.ts.tsp.R;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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.List;

import de.hdodenhof.circleimageview.CircleImageView;

public class UserAdapter extends RecyclerView.Adapter<UserAdapter.Viewholder>{


    private Context mContext;
    private List<User> mUsers;

    private FirebaseUser firebaseUser;

    public UserAdapter(Context mContext, List<User> mUsers) {
        this.mContext = mContext;
        this.mUsers = mUsers;
    }

    @NonNull
    @Override
    public Viewholder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(mContext) .inflate(R.layout.user_item, viewGroup, false);
        return new UserAdapter.Viewholder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final Viewholder viewHolder, int i) {
        firebaseUser = FirebaseAuth.getInstance().getCurrentUser();

        final User user = mUsers.get(i);

        viewHolder.btn_follow.setVisibility(View.VISIBLE);

        viewHolder.username.setText(user.getUsername());
        viewHolder.fullname.setText(user.getFullname());
        Glide.with(mContext) .load(user.getImageurl()) .into(viewHolder.image_Profile);
        isFollowing(user.getId(), viewHolder.btn_follow);

        if (user.getId().equals(firebaseUser.getUid())){

            viewHolder.btn_follow.setVisibility(View.GONE);

        }

        viewHolder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SharedPreferences.Editor editor = mContext.getSharedPreferences( "PREFS", Context.MODE_PRIVATE) .edit();
                editor.putString("profileid", user.getId());
                editor.apply();

                ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProfileFragment()).commit();
            }
        });

        viewHolder.btn_follow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (viewHolder.btn_follow.getText().toString().equals("follow")) {
                    FirebaseDatabase.getInstance().getReference().child("Follow").child(firebaseUser.getUid())
                            .child("following").child(user.getId()).setValue(true);
                    FirebaseDatabase.getInstance().getReference().child("Follow").child(user.getId())
                            .child("followers").child(firebaseUser.getUid()).setValue(true);
                } else {
                    FirebaseDatabase.getInstance().getReference().child("Follow").child(firebaseUser.getUid())
                            .child("following").child(user.getId()).removeValue();
                    FirebaseDatabase.getInstance().getReference().child("Follow").child(user.getId())
                            .child("followers").child(firebaseUser.getUid()).removeValue();

                }
            }
        });

    }

    @Override
    public int getItemCount() {
        return 0;
    }

    public class Viewholder extends RecyclerView.ViewHolder{

        public TextView username;
        public TextView fullname;
        public CircleImageView image_Profile;
        public Button btn_follow;

        public Viewholder(@NonNull View itemView) {
            super(itemView);

         username = itemView.findViewById(R.id.username);
         fullname = itemView.findViewById(R.id.fullname);
         image_Profile = itemView.findViewById(R.id.image_Profile);
         btn_follow = itemView.findViewById(R.id.btn_follow);
        }
    }

    private void isFollowing (final String userid, final Button button) {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference()
                .child("Follow").child(firebaseUser.getUid()).child("following");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.child(userid).exists()){
                    button.setText("following");
                } else {
                    button.setText("follow");
                }
            }

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

            }
        });
    }
}

希望有人能帮到你

最好的问候蒂姆·施密特

Answer 1

使用 orderby：

FirebaseDatabase.getInstance().getReference("Users").orderByChild("username")

您必须在特定字段上添加索引，在Firebase Database console 中更新您的规则。

{
   "rules": {
    // By default all nodes are private
    ".read":false,
    ".write":false,

    "Users": {
      ".read": true,
      ".write": "(auth!=null)",
      ".indexOn" : ["username"]
      }
   }
}

我建议使用 Cloud Firestore 而不是 Firebase 实时数据库。