Android Tutorial 415
The identifier matches up a Notification with any previous
Notification instances of that type. When the identifiers match, the
old Notification is updated instead of creating a new one. You might
have a Notification that some file is being downloaded. You could
update the Notification when the download is complete, instead of
filling the Notification queue with a separate Notification, which
quickly becomes obsolete. This Notification identifier only needs to
be unique within your application.
The notification displays as an icon and ticker text showing up on
the status bar. This is shown at the top of Figure.
Status bar notification showing an icon and ticker text.
Shortly after the ticker text displays,
the status bar returns to normal with
each notification icon shown. If the
users expand the status bar, they see
something like what is shown in Figure.