重复while循环不起作用-为什么？

Question

I want an imageView in my viewController to "pulsate", that means become bigger and then tinier again and repeat that until the "start"-button was pressed. The problem is, that every time I call that function in the viewDidLoad() with a repeat-while-loop, it has got a breakpoint for whatever reason.

That's the part of my viewDidLoad():

repeat {
   pulsate()
} while hasStarted == false

When I press the start button, hasStarted becomes true and it should stop pulsating. But it doesn't even start the function, it immediately calls an error. Where's the problem?

Here's my pulsate()-function

func pulsate()
{
    frameOR = imageView.frame
    frameNext = CGRect(x: imageView.frame.midX - 35, y: imageView.frame.midY - 35, width: 80, height: 80)
    let frameVDL = CGRect(x: imageView.frame.midX - 150, y: imageView.frame.midY - 150, width: 300, height: 300)

    if start == false
    {
        UIView.animate(withDuration: 2, animations: {
            self.imageView.frame = frameVDL
        }) { (finished) in
            UIView.animate(withDuration: 2, animations: {
                self.imageView.frame = self.frameOR
            }, completion: nil)
        }
    }
}

Thank your for your help! Have a great day!

Answer 1

You can use UIView.animate 's built-in options to really simplify what you're trying to do, and avoid locking up the thread.

Give this a try:

let frameOR = imageView.frame
let frameVDL = CGRect(x: imageView.frame.midX - 150, y: imageView.frame.midY - 150, width: 300, height: 300)

UIView.animate(withDuration: 2.0,
               delay: 0.0,
               options: [UIViewAnimationOptions.autoreverse, UIViewAnimationOptions.repeat],
               animations: {
                imageView.frame = frameVDL
                },
               completion: nil)

Your imageView should now be in a full "pulsing" loop, without needing any additional code. When you're ready to stop the animation, just call:

imageView.layer.removeAllAnimations()