Android App is not connecting to firebase realtime database in a real device

Question

I've asked a question before where my app was working only on the emulator but not a real device, here's a link of it:

Firebase database is not updating with no errors, slow response

unfortunately, I wasn't able to figure out the issue or solve it. So, I started from scratch and build a simple app that writes "TEST" to a real-time database, and the same issue was there, the app is working ONLY on the emulator but not my real device. So, I figured out that the app is not able to connect to firebase when I ran it in my device. But I couldn't figure out why?

Here's my main activity:

package com.example.alice.testingfirebase;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;


public class MainActivity extends AppCompatActivity {


    private DatabaseReference mDatabase;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mDatabase = FirebaseDatabase.getInstance().getReference();
        for (int i = 0; i<10;i++) {
            String id = i+"";
            mDatabase.child("users").child(id).setValue("TEST");
        }
    }
}

Here's my manifest:

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

    <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">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

and here's my build.gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.alice.testingfirebase"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0-rc02'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.google.firebase:firebase-core:16.0.1'
    implementation 'com.google.firebase:firebase-database:16.0.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

}
apply plugin: 'com.google.gms.google-services'

The rules of the database are set to be public.

After adding the INTERNET permission, the app keeps stopping, and here's part of the log cat:

09-09 14:39:55.374 21502-21537/com.example.alice.testingfirebase V/FA: Connection attempt already in progress
09-09 14:39:55.455 21502-21502/com.example.alice.testingfirebase D/AndroidRuntime: Shutting down VM
09-09 14:39:55.456 21502-21502/com.example.alice.testingfirebase E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.alice.testingfirebase, PID: 21502
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.alice.testingfirebase/com.example.alice.testingfirebase.MainActivity}: com.google.firebase.database.DatabaseException: Calls to setLogLevel() must be made before any other usage of FirebaseDatabase instance.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2955)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3030)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6938)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
     Caused by: com.google.firebase.database.DatabaseException: Calls to setLogLevel() must be made before any other usage of FirebaseDatabase instance.
        at com.google.firebase.database.FirebaseDatabase.zzb(Unknown Source:38)
        at com.google.firebase.database.FirebaseDatabase.setLogLevel(Unknown Source:3)
        at com.example.alice.testingfirebase.MainActivity.onCreate(MainActivity.java:22)
        at android.app.Activity.performCreate(Activity.java:7183)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2908)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3030) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6938) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374) 
09-09 14:39:55.472 21502-21551/com.example.alice.testingfirebase W/zygote64: Skipping duplicate class check due to unrecognized classloader
09-09 14:39:55.474 21502-21551/com.example.alice.testingfirebase I/DynamiteModule: Considering local module com.google.android.gms.firebase_database:4 and remote module com.google.android.gms.firebase_database:6
09-09 14:39:55.475 21502-21551/com.example.alice.testingfirebase I/DynamiteModule: Selected remote version of com.google.android.gms.firebase_database, version >= 6
09-09 14:39:55.506 21502-21551/com.example.alice.testingfirebase W/zygote64: Skipping duplicate class check due to unrecognized classloader
09-09 14:39:55.567 21502-21559/com.example.alice.testingfirebase D/NetworkSecurityConfig: No Network Security Config specified, using platform default
09-09 14:39:55.573 21502-21559/com.example.alice.testingfirebase D/TcpOptimizer: TcpOptimizer-ON
09-09 14:40:00.281 21502-21521/com.example.alice.testingfirebase I/zygote64: WaitForGcToComplete blocked for 22.520ms for cause HeapTrim
09-09 14:40:00.286 21502-21521/com.example.alice.testingfirebase W/zygote64: Suspending all threads took: 5.439ms

Answer 1

For developers using VIVO and OPPO phones, these brands have a strange problem connecting to Firebase. I have 7 devices of different makes and configurations for testing purposes and all of them connect except these two. There are no errors and no exceptions. They just refuse to connect. Just wanted to float this point out so developers using these phones know about the problem.

Answer 2

First, you don't have internet permission in your AndroidManifext.xml and I'm still wondering how it does works on the emulator.

Second, initialize FirebaseDatabase then DatabaseReference to be able to read-write data in Firebase Realtime database:

// Write a message to the database
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference().child("users").child("id"); //location to put, can be anything you want ...

myRef.setValue("TEST");

Also, are you sure this is what you want? Putting String in an id field? Consider checking your FireBase Database in console!

Read: https://firebase.google.com/docs/database/android/start

Answer 3

Please add this to your manifest file.

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.alice.testingfirebase">
        <uses-permission android:name="android.permission.INTERNET"/>
        <application
            android:allowBackup="true"..
            ....
        </application>
</manifest>

Also edit your MainActivity like

FirebaseDatabase obj= FirebaseDatabase.getInstance();
DatabaseReference mDatabase= obj.getReference();
for (int i = 0; i<10;i++) 
      {
         String id = i+"";
         mDatabase.child("users").child(id).setValue("TEST");
      }