How to use android pay api with nfc?

I am trying to implement "Tap and Pay(for payment transaction)" with NFC and android pay API.

I did not found any tutorial or example regarding the same.

I gone through http://developer.android.com/guide/topics/connectivity/nfc/hce.html but did not get it.

Above documentation talks about communicating with nfc using Host-based Card Emulation (i might be wrong)

How to achieve it ?? Any other APIs or i have to integrate PAYMENT PROTOCOL with Host-based Card Emulation Service?? like this

public class MyHostApduService extends HostApduService {
    @Override
    public byte[] processCommandApdu(byte[] apdu, Bundle extras) {

       //Implement PAYMENT protocol here
    }
    @Override
    public void onDeactivated(int reason) {
       ...
    }
}