Like the
UISwitch
we saw
here,
we do not have to specify a size for an
UIActivityIndicator.
It assumes a default size of
20 × 20
or 37 × 37,
depending on its
style.
The gear has 12 teeth.
The highlight starts at 9 o’clock
(12 o’clock in older versions of iOS)
and rotates clockwise once per second.
Hide the activity indicator when it has finished
so the user won’t think the app has stalled.
See
Activity
Indicator
in the
Human
Interface Guidelines.
The easiest way to center the
UIActivityIndicator
in the
View
was to move the
View’s
origin to the center of the
View.
The app remains motionles for three seconds,
rotates for 10 seconds,
and then stops.
This sequence is stage managed by the
view
controller.
The view controller manipulates the
view
like a marionette.
The strings are the
startAnimating
and
startAnimating
methods of the view.
An
NSTimer
is like an invisible
UIButton
that is automatically pressed after a certain number of seconds.
When the time is up,
it can send any message to any object.
Unlike the
performSelector:withObject:afterDelay:
we saw
here,
the timer can repeat itself automatically.
We will use this feature in the
next example.
main.mActivityAppDelegateViewControllerView