is user member of a group, show them categories [closed]

You should probably try this plugin first: http://buddydev.com/buddypress/blog-categories-for-groups-plugin/

Or you could take some code from it and try to implement that yourself. Start
with blog-categories-for-groups.php, and see the last few lines:

//for single post screen
function screen_group_blog_single_post(){
   global $bp;

   if(function_exists('bp_is_group')&&!bp_is_group())
      return;

    //do not catch the request for creating new post
   if(bp_is_action_variable('create',0))
           return;

   $current_group=groups_get_current_group();

   if(bcg_is_disabled($current_group->id))
           return;
   //if the group is private/hidden and user is not member, return
   if(($current_group->status=='private'||$current_group->status=='hidden')&&(!is_user_logged_in()||!groups_is_user_member(bp_loggedin_user_id(), $current_group->id)))
   return;//avoid prioivacy troubles

   if (bp_is_groups_component() && bp_is_current_action(BCG_SLUG) &&!empty($bp->action_variables[0]) ){

       $wpq=new WP_Query(bcg_get_query());
        if($wpq->have_posts()){
            //load template
         bp_core_load_template( apply_filters( 'groups_template_group_blog_single_post', 'bcg/home' ) );
        }
    else
        bp_core_add_message (__("Sorry, the post does not exists!","bcg"),"error");

   }
}

See also: http://buddypress.org/support/topic/how-to-exclude-a-group-from-the-groups-loop/