Animate alpha property on hover over - ios

Question

I have a collection of six seat objects (UIViews with the alpha property set to 0) on my screen and I have player objects basically placed on top of them. The seats may or may not have a player on top of it. What I have right now is I've programmed the player's touchesMoved event so that when I drag a player on top of a seat object the seat's alpha property will go from 0 to 0.6. And then while still dragging the player, if I drag him off the seat the alpha property will go back to 0.
Instead, is there a built in UIView animation that could instead cause the alpha property to kind of fluctuate back and forth between .6 and .2? Kind of a throbbing effect? Would this require core animation or something more advanced?
I'm using the following in the Player's touchesMoved method to drag a player and to detect if it's above a seat:
UITouch *aTouch = [touches anyObject];
self.center = [aTouch locationInView:[self.superview]];
Seat *seat = [controller seatAtPoint:[aTouch locationInView:self.superview]];
if (seat) {
self.hoverSeat = seat;
seat.alpha = .6;
} else {
self.hoverSeat.alpha = 0;
}
The seatAtPoint method in my controller is as follows:
- (Seat *) seatAtPoint:(CGPoint)point {
NSMutableArray seats = [NSMutableArray arrayWithCapacity:6];
for (int i = 1; i <= 6; i++) {
Seat *aSeat = (Seat*)[self.view viewWithTag:i];
[seats addObject:aSeat];
}
for (Seat *seat in seats) {
if (CGRectContainsPoint([seat frame], point)) {
return seat;
}
}
return nil;
}
I use a hoverSeat ivar to hold the seat above which the player is hovering. And then if the seat returned is nil then it sets that seat's alpha to 0.
A bug I'm seeing with this code is if I move the player around the screen a little too quickly sometimes the alpha property won't go back to 0. Can anyone think of a more effective way to ensure that it goes back to 0?
Thank you for any suggestions.

Answer 1

I would look into using CoreAnimation; it's not that hard to use. Here's what it might look like for a fade:
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:.5];
seat.alpha = 1;
[UIView commitAnimations];
You can look into the callbacks that methods like these use to create some kind of pulsing animation ( Trigerring other animation after first ending Animation (Objetive-C) ) when combined with a condition you can probably set it up to loop forever. Also of note is that UIView Animations disable user input when they're running ( Infinitely looping animation ).
As for the bug you mentioned, if it's still happening, you could set up a timer that when fired, iterates through all the seats and checks for ones that aren't being displayed correctly. You might want to set this interval to be pretty infrequent so that it doesn't interrupt or impact the performance of your other animations.