Question

So basically, I have this timer that should be repeated when it receives a key event, and invalidates when the user releases the key. However, I am unable to “validate” the timer back even by calling the addTimer:forMode: in NSRunLoop. Does anyone know why this is happening and how I can fix this? Thanks.

Answer 1

You cannot use invalidated timer.

From Apple Docs:

Once scheduled on a run loop, the timer fires at the specified
interval until it is invalidated. A non-repeating timer invalidates
itself immediately after it fires. However, for a repeating timer, you
must invalidate the timer object yourself by calling its invalidate
method. Calling this method requests the removal of the timer from the
current run loop; as a result, you should always call the invalidate
method from the same thread on which the timer was installed.
Invalidating the timer immediately disables it so that it no longer
affects the run loop. The run loop then removes and releases the
timer, either just before the invalidate method returns or at some
later point. Once invalidated, timer objects cannot be reused.