java - 只打印特定信息到String

Question

我有一个 Firebase 应用，可以使用数据快照从 Firebase 实时数据库返回用户 UID 和分数。

当我运行此代码时:

package com.example.securityapp;


import androidx.appcompat.app.AppCompatActivity;

import android.nfc.Tag;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

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.Query;
import com.google.firebase.database.ValueEventListener;

import static java.lang.System.in;

public class leaderboard extends AppCompatActivity {

    DatabaseReference databaseUsers;
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    FirebaseAuth mAuth;
    TextView score;
    private static final String TAG = "leaderboard";
    String s;





    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_leaderboard);

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser user = mAuth.getCurrentUser();
        score = (TextView) findViewById(R.id.tableText);

        leaderBoard();




    }

    public void leaderBoard(){
        database.getReference().child("Scores").addValueEventListener(new ValueEventListener() {
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    System.out.println("The score is: " + snapshot.toString());
                    s = s + snapshot.toString() + "\n";
                    score.setText(s);
                }



            }


            @Override
            public void onCancelled(DatabaseError databaseError) {
                // Getting Post failed, log a message
                Log.w(TAG, "loadPost:onCancelled", databaseError.toException());

            }


        });

    }


}

我得到的结果是:

有没有办法只返回键值和点值，而不返回随之而来的所有其他信息？

排行榜屏幕的当前状态:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        tools:context=".leaderboard">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="0.38">

            <TextView
                android:layout_width="420dp"
                android:layout_height="150dp"
                android:gravity="center"
                android:text="Leaderboard!"
                android:textAppearance="@style/TextAppearance.AppCompat.Body1"
                android:textColor="#0C40F1"
                android:textSize="50dp"
                android:textStyle="bold">

            </TextView>
        </RelativeLayout>

        <TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            >
            <TableRow>
                <TextView
                    android:text="User ID"
                    android:padding="3dip"
                    android:layout_gravity="center"
                    android:textSize="20dp"/>
                <TextView
                    android:text="Points"
                    android:layout_gravity="center"
                    android:gravity="right"
                    android:textSize="20dp"/>
            </TableRow>
            <TableRow>
                <TextView
                    />
            </TableRow>
            <TableRow>
                <TextView
                    android:id="@+id/tableText"
                    android:layout_weight="1"/>
            </TableRow>
        </TableLayout>
    </LinearLayout>



</ScrollView>

谢谢

Answer 1

您正在加载整个 Scores 节点，但显然只想显示每个子节点的单个属性的值。在这种情况下，您可以使用以下内容查找该属性的值:

database.getReference().child("Scores").addValueEventListener(new ValueEventListener() {
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
            System.out.println("The score is: " + snapshot.child("Points").getValue());
            s = s + snapshot.toString() + "\n";
            score.setText(s);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});