How does Host-based Card Emulation deal with AID (Application ID)?

Question

I am gonna write a Payment Application based on Host-Based Card Emulation(HCE) of Android 4.4 (Kitkat) but I don't understand a process between AID (Application ID) and HCE service of Android 4.4 after I read this article Host-based Card Emulation. After we register an Application ID of both "Payment" and "Other" Category in the manifest file, Where else is the AID used? or It is used for Our written HCE service to recognize and then do whatever that define in our written HCE Service?

Halverson

Answer 1

or It is used for Our written HCE service to recognize and then do whatever that define in our written HCE Service?

This is the case. You register your AID in the manifest file. If a reader selects your AID the NfcService then knows which HCE-service to start and to dispatch APDU transfers to.

All further communication will then get routed to your HCE Service until the reader selects a different AID or the reader stops providing the RF field.

Leone

until the reader selects a different AID or the reader stops providing the RF field - You mean a different AID of a different HCE-Service? – Halverson