It doesn't affect only PPAs, it affects all sources changes.
Also closing and reopening software-center isn't enough to make it aware of new sources.
The following allows me to immediately see the new source:
<add any source, not just a PPA one>
apt-get update
update-apt-xapian-index
software-center
If I omit update-apt-xapian-index, then software-center is not informed about the changes until much later on, maybe until update-apt-xapian-index is launched from /etc/cron.daily/apt.
It doesn't affect only PPAs, it affects all sources changes.
Also closing and reopening software-center isn't enough to make it aware of new sources.
The following allows me to immediately see the new source:
<add any source, not just a PPA one> apt-xapian- index
apt-get update
update-
software-center
If I omit update- apt-xapian- index, then software-center is not informed about the changes until much later on, maybe until update- apt-xapian- index is launched from /etc/cron. daily/apt.