Start Sticky Service on Boot in Android

BroadcastReceiverOnBootComplete.java

public class BroadcastReceiverOnBootComplete extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equalsIgnoreCase(Intent.ACTION_BOOT_COMPLETED)) {
            Intent serviceIntent = new Intent(context, AndroidServiceStartOnBoot.class);
            context.startService(serviceIntent);
        }
    }
}

AndroidServiceStartOnBoot.java

public class AndroidServiceStartOnBoot extends Service {

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
       // here you can add whatever you want this service to do
    }

}

AndroidManifest.xml

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

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

    <receiver
        android:name="com.javacodegeeks.androidserviceonbootexample.BroadcastReceiverOnBootComplete"
        android:enabled="true"
        android:exported="false">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
        </intent-filter>
        <intent-filter>
            <action android:name="android.intent.action.PACKAGE_REPLACED" />
            <data android:scheme="package" />
        </intent-filter>
        <intent-filter>
            <action android:name="android.intent.action.PACKAGE_ADDED" />
            <data android:scheme="package" />
        </intent-filter>
    </receiver>

    <service android:name="com.javacodegeeks.androidserviceonbootexample.AndroidServiceStartOnBoot"></service>

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

        <activity
            android:name="com.javacodegeeks.androidserviceonbootexample.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>
    </application>

</manifest
>

if we want to be sure our service is sticky

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {

        if (workerThread == null) {
            workerThread = Thread(run)
            workerThread!!.start()

            Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
        }

        return Service.START_STICKY
    }

and

    override fun onTaskRemoved(rootIntent: Intent?) {
        val restartService = Intent(applicationContext,
                this.javaClass)
        restartService.`package` = packageName
        val restartServicePI = PendingIntent.getService(
                applicationContext, 1, restartService,
                PendingIntent.FLAG_ONE_SHOT)
        val alarmService = applicationContext.getSystemService(Context.ALARM_SERVICE) as AlarmManager
        alarmService.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + 5000, restartServicePI)
    }

References
http://blog.vogella.com/2011/12/11/automatically-starting-services-in-android-after-booting/
https://examples.javacodegeeks.com/android/core/activity/android-start-service-boot-example/
http://www.framentos.com/en/android-tutorial/2012/08/01/how-to-start-a-service-at-boot-in-android/