如何在 Swift 中为 UIImages 创建闪烁的指针效果

Question

我正在尝试在 Swift 中创建指针效果。我有六个 UIImageView，每个都有一个以循环方式排序的 UIImage。我想创建一个动画，让每个图像在一定时间内闪烁（好像它是指针指示）。

我想用图像的透明版本创建一个数组，然后从中创建一个动画序列，但持续时间搞混了。

这就是我想要实现的想法。我希望图像有这种闪烁的效果，一张一张。

Answer 1

这就是我如何完成将视图放置在一个圆圈中并使它们成为 "flash"..

首先我创建了常规视图（我不想使用 ImageView，但您可以随意更改代码）..
我计算了视图需要围绕具有一定半径的中心点放置的角度..以使它们放置在一个圆圈中。
接下来我创建一个动画函数，它有正向和反向动画（我无法使 autoreverses 标志起作用）..
为了让一个接一个显示，我只需添加一个延迟（x2 因为正向 + 反向）..
为了弄清楚所有动画何时完成，我将整个函数包装在 CATransaction.

注意：如果您不需要循环放置代码，只需将其删除即可。 AFAIK，你只需要动画代码。

//
//  ViewController.swift
//  TestSO
//
//  Created by Brandon on 2018-03-03.
//  Copyright © 2018 XIO. All rights reserved.
//

import UIKit

extension UIColor {
    class func random() -> UIColor {
        let rand = { (max: CGFloat) -> CGFloat in
            let rnd = CGFloat(arc4random()) / CGFloat(UInt32.max)
            return rnd * max
        }

        return UIColor(red: rand(1.0), green: rand(1.0), blue: rand(1.0), alpha: 1.0)
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let makeView = { () -> UIView in
            let view = UIView()
            view.backgroundColor = UIColor.random()
            view.frame = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
            self.view.addSubview(view)
            return view
        }

        let imageViews = [
            makeView(),
            makeView(),
            makeView(),
            makeView(),
            makeView(),
            makeView()
        ]

        let locationForView = { (angle: CGFloat, center: CGPoint, radius: CGFloat) -> CGPoint in
            let angle = angle * CGFloat.pi / 180.0
            return CGPoint(x: center.x - radius * cos(angle), y: center.y + radius * sin(angle))
        }

        for i in 0..<imageViews.count {
            let center = self.view.center
            let radius = ((150.0 + imageViews[i].bounds.size.width) / 2.0)
            let count = imageViews.count
            imageViews[i].center = locationForView(((360.0 / CGFloat(count)) * CGFloat(i)) + 90.0, center, radius)
        }

        self.animate(views: imageViews.reversed(), duration: 3.0, intervalDelay: 0.5)
    }

    private func animate(views: [UIView], duration: TimeInterval, intervalDelay: TimeInterval) {

        CATransaction.begin()
        CATransaction.setCompletionBlock {
            print("COMPLETED ALL ANIMATIONS")
        }

        var delay: TimeInterval = 0.0
        let interval = duration / TimeInterval(views.count)

        for view in views {
            let colour = view.backgroundColor
            let transform = view.transform

            UIView.animate(withDuration: interval, delay: delay, options: [.curveEaseIn], animations: {

                view.backgroundColor = UIColor.red
                view.transform = CGAffineTransform(scaleX: 1.2, y: 1.2)

            }, completion: { (finished) in

                UIView.animate(withDuration: interval, delay: 0.0, options: [.curveEaseIn], animations: {

                    view.backgroundColor = colour
                    view.transform = transform

                }, completion: { (finished) in


                })
            })

            delay += (interval * 2.0) + intervalDelay
        }
        CATransaction.commit()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

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