Facebook import contact, avoid the ones already imported

Question

I want to write an app to enable Facebook (or Gmail, twitter,etc) import contact. When the second time the user use import contact, I should not show the contacts that they already imported. Is there any efficient solution to this?

Answer 1

Yes, this is possible, but you need to keep a records yourself of what contacts you've imported. Facebook/Twitter does not maintain lists of who you've imported.

Simply import them all, and then discard the ones that you've previously seen before.