How to pass the "request code" when doing authentication

The auth flow works a bit differently between the two SDKs. You can find instructions for setting up the auth flow in the Core SDK here:

https://www.dropbox.com/developers/core/start/android#authenticating

You use the authenticationSuccessful method to check if the user is coming back from the app auth flow. If not, it will return false so your app doesn't run the rest of that code again.

Thank you Greg. Let me ask you about this scenario then. Let's say that in my app the user wants to backup a file. So the app initiates authentication, on resume is called and the file gets backed up. Good, now let's say right away the user press home button and come back to the app, the on resume will be called. In that case, won't the authenticationSuccessfull returns true? And if so then the file will get backup again (and the file could've changed meanwhile).
IIn summary, is it guaranteed that the authenticationSuccessfull will return true "only" if the on resume is called as a result Auth flow and will return false even if authentication was just done previously on the same activity?

Thank you again

Your summary is correct, authenticationSuccessful only returns true right after the auth flow. Simply returning to the app normally won't have it return true.

How to perform this check using API v2?

Allek, are you using the Dropbox Java SDK for API v2 on Android? If so, there's a sample that shows the authorization flow here:

https://github.com/dropbox/dropbox-sdk-java/tree/master/examples/android