android pay 对nfc要求,How to use android pay api with nfc?

Comment from icyerasor is completely right. If you want to pay for something with Android pay and NFC, you should use Android Pay application. You can't implement custom payment application because of security issues (for example, google doesn't allow Android pay on rooted devices or on devices with custom screen locks).

As for Android Pay API - it is designed to pay without any NFC terminal - only from your application. You can see typical payment flows here - those can't include any NFC contacts.

If you wonder, what is NFC card emulation designed for - it can be used for person identification instead of cards, for storing bus tickets and etc. I think that it is possible to make a custom payment system - but it will require creating custom bank processing and NFC terminals (card readers) at least (I repeat once again that you can't use Android Pay). That's almost impossible for a little company which business isn't in this field (very expensive, requires lots of licensing work and time). And even after it, your application will be banned in google play.