CODEWITHSUNDEEP
iosswiftxcodeexception
ammar arangy
ammar arangy

Reputation: 95

iOS Recursive Animation Exception

I have a cell with counter with tow dots ":" that blinks, here is the blink code:

func blinkLable(){

        if blinkingLabel.alpha == 1 {

            UIView.animateWithDuration(1, animations: {

                self.blinkingLabel.alpha = 0

                }, completion: { (true) in

                    UIView.animateWithDuration(1, animations: {

                        self.blinkingLabel.alpha = 1

                        }, completion: { (true) in

                            self.blinkLable()
                    })

            })
        }
    }

This function is called on awakeFromNib function of nib, after I submitted the app to store sometimes i got this weird exception:

Crashed: com.apple.main-thread
0  libobjc.A.dylib                0x19412bbd0 objc_msgSend + 16
1  UIKit                          0x18709bbfc +[UIView(UIViewAnimationWithBlocks) animateWithDuration:animations:completion:] + 64
2  RTA                            0x100df3374 TimeReminingCell.(blinkLable() -> ()).(closure #2).(closure #2) (TimeReminingCell.swift:73)
3  UIKit                          0x186f5855c -[UIViewAnimationBlockDelegate _didEndBlockAnimation:finished:context:] + 408
4  UIKit                          0x186f580c4 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 188
5  UIKit                          0x186f57fcc -[UIViewAnimationState animationDidStop:finished:] + 104
6  QuartzCore                     0x18686162c CA::Layer::run_animation_callbacks(void*) + 296
7  libdispatch.dylib              0x194795954 _dispatch_client_callout + 16
8  libdispatch.dylib              0x19479a20c _dispatch_main_queue_callback_4CF + 1608
9  CoreFoundation                 0x18245b544 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
10 CoreFoundation                 0x1824595ec __CFRunLoopRun + 1492
11 CoreFoundation                 0x182384f74 CFRunLoopRunSpecific + 396
12 GraphicsServices               0x18bde76fc GSEventRunModal + 168
13 UIKit                          0x186f86d94 UIApplicationMain + 1488
14 RTA                            0x100943fe0 main (AppDelegate.swift:35)
15 libdyld.dylib                  0x1947c2a08 start + 4

Pleas any help with this problem

Upvotes: 2

Views: 798

Answers (3)

Jogendar Choudhary
Jogendar Choudhary

Reputation: 3494

You have to use animation options:

UIView.animate(withDuration: 0.1, delay: 0, options: UIViewAnimationOptions.repeat, animations: {
        self.blinkingLabel.alpha = 0;

    }, completion: { (bool) in
        self.blinkingLabel.alpha = 1;

    })

Upvotes: 0

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726479

Recursive animation error happens because your animation is, well, recursive: the innermost completion block of the code in blinkLable() invokes blinkLable(), completing the recursive chain.

There is no need to do that, however, because UIView animation supports repetitions:

func blinkLable() {
    UIView.animateWithDuration(1, delay: 0, options: [.repeat], animations: {
        self.blinkingLabel.alpha = 1 - self.blinkingLabel.alpha
    }, completion: nil)
}

The value of 1 - alpha is zero when alpha is one, and one when alpha is zero.

Upvotes: 3

Max Pevsner
Max Pevsner

Reputation: 4104

What you have here is a classical stack overflow. You invoke the same function from itself forever.

Instead you need to repeat the animation:

UIView.animate(withDuration: 1.0, delay: 0, options: [.repeat, .autoreverse], animations: {
    self.blinkingLabel.alpha = 0
}, completion: nil)

Upvotes: 0

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