Firebase+Android sample app with background Service + local notifications.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bgfirebaseapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="17" />

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

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.bgfirebaseapp.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

        <service
            android:name=".FirebaseBackgroundService"
            android:exported="false"
            android:process=":remote" >
            <intent-filter>
                <action android:name="com.example.bgfirebaseapp.FirebaseBackgroundService" />
            </intent-filter>
        </service>

        <receiver android:name=".StartFirebaseAtBoot" >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" >
                </action>
            </intent-filter>
        </receiver>
    </application>

</manifest>

FirebaseBackgroundService.java

package com.example.bgfirebaseapp;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;

import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.ValueEventListener;

public class FirebaseBackgroundService extends Service {
	
	private Firebase f = new Firebase("https://somedemo.firebaseio-demo.com/");
	private ValueEventListener handler;

	@Override
	public IBinder onBind(Intent arg0) {
		return null;
	}
	
	@Override
	public void onCreate() {
		super.onCreate();
		
		handler = new ValueEventListener() {
			@Override
			public void onDataChange(DataSnapshot arg0) {
				postNotif(arg0.getValue().toString());
			}
			
			@Override
			public void onCancelled() {
			}
		};
		
		f.addValueEventListener(handler);
	}

	private void postNotif(String notifString) {
		NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
		int icon = R.drawable.ic_launcher;
		Notification notification = new Notification(icon, "Firebase" + Math.random(), System.currentTimeMillis());
//		notification.flags |= Notification.FLAG_AUTO_CANCEL;
		Context context = getApplicationContext();
		CharSequence contentTitle = "Background" + Math.random();
		Intent notificationIntent = new Intent(context, MainActivity.class);
		PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent, 0);
		notification.setLatestEventInfo(context, contentTitle, notifString, contentIntent);
		mNotificationManager.notify(1, notification);
	}

}

MainActivity.java

package com.example.bgfirebaseapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		// Start the background Firebase activity
		startService(new Intent(FirebaseBackgroundService.class.getName()));
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

Screen Shot 2013-08-06 at 5.05.57 PM.png

StartFirebaseAtBoot.java

package com.example.bgfirebaseapp;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

/**
 * Start the service when the device boots.
 * 
 * @author vikrum
 *
 */
public class StartFirebaseAtBoot extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		context.startService(new Intent(FirebaseBackgroundService.class.getName()));
	}
}

Hi @gthb619 @vikrum,
Thank you to share your knowledge with us. I am just confuse on this point what to do and follow.
Like as you said follow this

Use this
startService(new Intent(this, FirebaseBackgroundService.class));

instead of this

startService(new Intent(FirebaseBackgroundService.class.getName()));

StartFirebaseAtBoot.java:
Use this

context.startService(new Intent(context, FirebaseBackgroundService.class));

instead of this

context.startService(new Intent(FirebaseBackgroundService.class.getName()));

So, to follow above mentioned suggestion by @gthb619 does I have to remove this

<service
            android:name=".FirebaseBackgroundService"
            android:exported="false"
            android:process=":remote" >
            <intent-filter>
                <action android:name="com.example.bgfirebaseapp.FirebaseBackgroundService" />
            </intent-filter>
        </service>

        <receiver android:name=".StartFirebaseAtBoot" >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" >
                </action>
            </intent-filter>
        </receiver>

Someone can tell me what is the right way to do nowadays.

Thank you

One other solution is using server side Firebase Functions

Functions can be implemented to monitor database events and send cloud messages.

Then a FirebaseMessagingService service can be implemented in the Android app to listen for "com.google.firebase.MESSAGING_EVENT" sent from the funtion.

If notification field is set null the message can even awake the service even if system is in doze mode. Best strategy is then to create a notification. Keep it short and exit. Each message will start the service so no wories.

The Cloud message HTTP body sent from the server function would look like this

{
   "registration_ids":[
      "user_token_0_here", "user_token_n_here", "and so on"
   ],
   "notification":null,
   "data":{
      "par1":"AAA",
      "par2":"BBB",
      "par3":"CCC"
   },
   "android":null,
   "webpush":null,
   "priority":10
}

The AndroidManifest.xml may have the service declared like this:

<service
        android:name=".SimpleFirebaseMessagingService"
        android:exported="false">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT"/>
    </intent-filter>
</service>

Full details Set up a Firebase Cloud Messaging client app on Android

You are calling the service once by receiver and once by main activity is there a chance the same service is started twice?