Facebook sdk problem (android)

Hi!

I set up the facebook sdk like it showed me on the tutorial (for android). When I test it on my phone and I would like to log in it says that “Invalid key hash. “Random key hash” doesn not match any stored key hashes. Configure your app key hashes at http:\…”

Where I write “Random key hash” it is a combination of letters and numbers but I never used this hash and on the app’s page under setting I’ve got a different key hash.

What should I do?

So It worked once and then the same error message…Why?