Introduction to Broadcast receiver

A Broadcast receiver is an Android component which allows you to register for system or application events.

A receiver can be registered via the AndroidManifest.xml file or dynamically via the Context.registerReceiver() method.

public class MyReceiver extends BroadcastReceiver {
   @Override
   public void onReceive(Context context, Intent intent) {
      //Your implementation goes here.
   }
}

Here I have taken an example of ACTION_BOOT_COMPLETED which is fired by the system once the Android has completed the boot process.

You can register a reciever in manifest file like this:

<application
   android:icon="@drawable/ic_launcher"
   android:label="@string/app_name"
   android:theme="@style/AppTheme" >
   <receiver android:name="MyReceiver">
      <intent-filter>
         <action android:name="android.intent.action.BOOT_COMPLETED">
         </action>
      </intent-filter>
   </receiver>
</application>

Now device gets booted, onReceive() method will be called and then you can do your work (e.g. start a service, start an alarm).