Android : How to implement background service for chromecast in android

I have referred https://github.com/ovingalafsal/ChromeCastSampleApp for casting media file using default receiver and default media channel and i have integrated into my existing app which is working fine but which is not running in background when press the home button and lock the phone also. so I want to implement the background service for this, while casting media file with default receiver. So Please guide me to how to handle the background service for casting and create the notification and handle in lock state of the phone. Would be grateful if give any sample or demo for this.

You can refer the code from this https://github.com/ovingalafsal/ChromeCastSampleApp.

Thanks in Advance