Xcode Swift-对UIImageView进行重复动画处理

Question

just quick inquiry in regards to implementing an issue I'm having with animating a UIImageView. I successfully implemented animating an image to slide off screen; but i want it to reappear when it exists the view to simulate a side-scroller game animation.

Something like this:

I've tried implementing a completion handler but struggled understanding the logic of how to implement it, so I removed my attempts; so my code is left as follows:

let oldCenter = background.center
        let newCenter = CGPoint(x: oldCenter.x - 400, y: oldCenter.y)

        UIView.animate(withDuration: 2, delay: 0, options: .curveLinear, animations: {
            self.background.center = newCenter
        }) { (success: Bool) in
            print("Done moving image")
        }

An example or pointers on how to achieved my desired animation would be appreciated!

Answer 1

let oldCenter = view.center
    let newCenter = CGPoint(x: oldCenter.x - 400, y: oldCenter.y)
    UIView.animate(withDuration: 2.0, delay: 0.0, options: 
    [.curveLinear, .repeat], animations: {
      view.center = newCenter
    }, completion: nil)

Answer 2

If you want to repeat the animation, there is no need to implement the completion . animate(withDuration:delay:options:animations:completion:) has options parameter ( UIViewAnimationOptions ), which is:

A mask of options indicating how you want to perform the animations. For a list of valid constants, see UIViewAnimationOptions.

One of the constants for the UIViewAnimationOptions is repeat :

Repeat the animation indefinitely.

So, what you should do:

UIView.animateKeyframes(withDuration: 2.0, delay: 0.0, options: [.curveLinear, .repeat], animations: {
    self.background.center = newCenter
}, completion: nil)

Again, implementing completion is not required for repeating the animation, implementing it is up to your case.

Answer 3

You can try UIView UIView repeat option

    let oldCenter = background.center
    let newCenter = CGPoint(x: oldCenter.x - 400, y: oldCenter.y)

    UIView.animate(withDuration: 2, delay: 0, options: [.curveLinear, repeat], animations: {
        self.background.center = newCenter
    }) { (success: Bool) in
        print("Done moving image")
        if(success)
        {
          self.background.center = oldCenter
        }
    }