无法从Firebase实时数据库读取数据，应用已连接求解决

我尝试从Firebase实时数据库提取数据并显示在TextView中，但始终无法成功。应用已成功连接Firebase（日志显示：设备解锁：为[DEFAULT]应用初始化所有Firebase API。FirebaseApp初始化成功），使用模拟器运行且设备有网络。我尝试了调试模式、新建项目及Firebase实时数据库，还尝试将数据打印到日志中，但均无效果，也没有报错信息。

MainActivity.java #

package com.example.test;

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

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

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;

public class MainActivity extends AppCompatActivity {

    private TextView textView;

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

        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference userRef = database.getReference("Data");

        textView = findViewById(R.id.textView);

        userRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                String value = dataSnapshot.getValue(String.class);
                textView.setText(value);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Log.e("Firebase", "Failed to read value.", databaseError.toException());
            }
        });
    }
}

build.gradle(Project:Test) #

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
repositories {
google()
mavenCentral()  // Maven Central repository
}
dependencies {
classpath 'com.android.tools.build:gradle:8.0.2'
classpath 'com.google.gms:google-services:4.3.15'
}
}

allprojects {
    repositories {
        google()
        mavenCentral()  // Maven Central repository
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle(Module:app) #

plugins {
    id 'com.android.application'
    id 'com.google.gms.google-services'
}

android {
    compileSdkVersion 33

    defaultConfig {
        applicationId "com.example.test"
        minSdkVersion 21
        targetSdkVersion 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    namespace 'com.example.test'

}

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.3.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'com.google.firebase:firebase-database:20.2.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test.ext:junit:1.1.5'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
}

activity_main.xml #

<androidx.constraintlayout.widget.ConstraintLayout      xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<TextView
    android:id="@+id/textView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    android:text="Retrieve Data"
    android:textAlignment="center"
    android:textColor="@color/colorPrimaryDark"
    android:textSize="18sp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml #

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.test">

<uses-permission android:name="android.permission.INTERNET" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">

    <activity android:name=".MainActivity"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

内容的提问来源于stack exchange，提问作者shakhmiev