Thank you @tsangwailam and @jeff for your time to help me. I really appreciate that.
I just copied the sample provided by jeff, but I'm still unable to make it work. When I start the app it shows me the following log in the output:
and when I hit the first enabled button, it just crashes the app. I don't know what the hell is wrong with it, but I'm really frustrated to develop with Facebook platform, it really sucks!