Android : android - post to facebook group

i am new to facebook api , i follow this tutorial to post to my wall and its work

but i need to post to group

i add user_groups and user_likes

if (!facebook.isSessionValid()) {
                facebook.authorize(this,
                        new String[] { "email", "publish_stream","user_likes" , "user_groups" },

any one can help me thank you in advance