Swift UIView animateWithDuration completion closure called immediately

问题

I'm expecting the completion closure on this UIView animation to be called after the specified duration, however it appears to be firing immediately...

 UIView.animateWithDuration(
        Double(0.2),
        animations: {
            self.frame = CGRectMake(0, -self.bounds.height, self.bounds.width, self.bounds.height)
        },
        completion: { finished in
            if(finished) {
                self.removeFromSuperview()
            }
        }
    )

Has anyone else experienced this? I've read that others had more success using the center rather than the frame to move the view, however I had the same problems with this method too.

回答1:

For anyone else that is having a problem with this, if anything is interrupting the animation, the completion closure is immediately called. In my case, this was due to a slight overlap with a modal transition of the view controller that the custom segue was unwinding from. Using the delay portion of UIView.animateWithDuration(0.3, delay: 0, options: UIViewAnimationOptions.CurveEaseInOut, animations:{} had no effect for me. I ended up using GCD to delay animation a fraction of a second.

// To avoid overlapping with the modal transiton
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(0.2 * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), {

    // Animate the transition
    UIView.animateWithDuration(0.3, delay: 0, options: UIViewAnimationOptions.CurveEaseInOut, animations: {

         // Animations

         }, completion: { finished in

         // remove the views
         if finished {            
             blurView.removeFromSuperview()
             snapshot.removeFromSuperview()
         }
    })
})

回答2:

I resolved this in the end by moving the animation from hitTest() and into touchesBegan() in the UIView

来源：https://stackoverflow.com/questions/25626515/swift-uiview-animatewithduration-completion-closure-called-immediately