How can non-Coinbase customers pay to Coinbase from Android? Scenario: Say I want to create a shopping app on android. After filling the shopping cart, when the user wants to check out, he is asked to pay me the bitcoins.

I have created an account on Coinbase.com.

Questions: After adding the items in the app to the cart, the user is directed to the coinbase payment page. How is the user going to pay me, if he doesn't have a Coinbase account but some other wallet? If he pays me the required bitcoins, how will I relate the user's payment with the invoice of the order generated for him?
The coinbase payment page has a "pay to address" option that will generate a unique address associated with your order and display a QR code. User can simply send payment to that address.