Android Starting Service at Boot Time , How to restart service class after device Reboot?

Your receiver:

public class MyReceiver extends BroadcastReceiver {   

    @Override
    public void onReceive(Context context, Intent intent) {

     Intent myIntent = new Intent(context, YourService.class);
     context.startService(myIntent);

    }
}

Your AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.broadcast.receiver.example"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="true">

        <activity android:name=".BR_Example"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    <!-- Declaring broadcast receiver for BOOT_COMPLETED event. -->
        <receiver android:name=".MyReceiver" android:enabled="true" android:exported="false">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>

    </application>

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

</manifest>

Create a BroadcastReceiver and register it to receive ACTION_BOOT_COMPLETED. You also need RECEIVE_BOOT_COMPLETED permission.

Read: Listening For and Broadcasting Global Messages, and Setting Alarms

It's possible to register your own application service for starting automatically when the device has been booted. You need this, for example, when you want to receive push events from a http server and want to inform the user as soon a new event occurs. The user doesn't have to start the activity manually before the service get started...

It's quite simple. First give your app the permission RECEIVE_BOOT_COMPLETED. Next you need to register a BroadcastReveiver. We call it BootCompletedIntentReceiver.

Your Manifest.xml should now look like this:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.jjoe64">
 <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
 <application>
  <receiver android:name=".BootCompletedIntentReceiver">
   <intent-filter>
    <action android:name="android.intent.action.BOOT_COMPLETED" />
   </intent-filter>
  </receiver>
  <service android:name=".BackgroundService"/>
 </application>
</manifest>

As the last step you have to implement the Receiver. This receiver just starts your background service.

package com.jjoe64;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;

import com.jjoe64.BackgroundService;

public class BootCompletedIntentReceiver extends BroadcastReceiver {
 @Override
 public void onReceive(Context context, Intent intent) {
  if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) {
   Intent pushIntent = new Intent(context, BackgroundService.class);
   context.startService(pushIntent);
  }
 }
}

From http://www.jjoe64.com/2011/06/autostart-service-on-device-boot.html