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()));
	}
}

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?