ios - UIPageControl View subview 中为 nil

Question

我是 ios swift 的新手，想通过图像更改 UIPageControl 点的大小。我在这里发现了同样的问题(UIPageControl custom class - found nil changing image to the dots)但似乎答案是错误的，仍然在页面控制 View subview (UIImageView)为零

由于我没有足够的声誉，所以必须在这里提问。

这是我如何将 ImageView 添加到 ScrollView

let imgOne = UIImageView(frame: CGRectMake(0, 0,scrollViewWidth, scrollViewHeight))
imgOne.image = UIImage(named: "1")
let imgTwo = UIImageView(frame: CGRectMake(scrollViewWidth, 0,scrollViewWidth, scrollViewHeight))
imgTwo.image = UIImage(named: "2")
let imgThree = UIImageView(frame: CGRectMake(scrollViewWidth*2, 0,scrollViewWidth, scrollViewHeight))
imgThree.image = UIImage(named: "3")
let imgFour = UIImageView(frame: CGRectMake(scrollViewWidth*3, 0,scrollViewWidth, scrollViewHeight))
imgFour.image = UIImage(named: "4")

self.scrollView.addSubview(imgOne)
self.scrollView.addSubview(imgTwo)
self.scrollView.addSubview(imgThree)
self.scrollView.addSubview(imgFour)

下面是问题的答案

class PageControl: UIPageControl {
    var activeImage: UIImage!
    var inactiveImage: UIImage!
    override var currentPage: Int {
        willSet {
            self.updateDots()
        }
    }

    convenience init(activeImage: UIImage, inactiveImage: UIImage) {
        self.init()

        self.activeImage = activeImage
        self.inactiveImage = inactiveImage

        self.pageIndicatorTintColor = UIColor.clearColor()
        self.currentPageIndicatorTintColor = UIColor.clearColor()
    }

    func updateDots() {
        for var i = 0; i < count(subviews); i++ {
            var view: UIView = subviews[i] as! UIView
            if count(view.subviews) == 0 {
                self.addImageViewOnDotView(view, imageSize: activeImage.size)
            }
            var imageView: UIImageView = view.subviews.first as! UIImageView // nil
            imageView.image = self.currentPage == i ? activeImage : inactiveImage
        }
    }

    // MARK: - Private

    func addImageViewOnDotView(view: UIView, imageSize: CGSize) {
        var frame = view.frame
        frame.origin = CGPointZero
        frame.size = imageSize

        var imageView = UIImageView(frame: frame)
        imageView.contentMode = UIViewContentMode.Center
        view.addSubview(imageView)
    }

}

Answer 1

花了几天时间，我通过以下方式解决了这个问题......不知道解决方案怎么样，欢迎改进...有 2 个问题

1:在函数 updateDots 中，应该如下所示

func updateDots() {
    for var i = 0; i < subviews.count; i++ {
        var imageView: UIImageView? = nil
        let view: UIView = subviews[i]
        if (view.subviews.first is UIImageView) {
            if (subviews.count == 0) {
                addImageViewOnDotView(view, imageSize: activeImage.size)
            }
            imageView = (view.subviews.first as! UIImageView)
            imageView!.image = self.currentPage == i ? activeImage : inactiveImage
        }

        if (imageView == nil) {
            imageView = UIImageView(frame: CGRectMake(0.0, 0.0, view.frame.size.width, view.frame.size.height));
            imageView!.image = self.currentPage == i ? activeImage : inactiveImage
            view.addSubview(imageView!)
        }
    }
}

2:调用此函数时，应该在(didSet)滚动之后而不是在(willSet)之前

override var currentPage: Int {
    didSet {
        self.updateDots()
    }
}