UIPageControl自定义类 – 发现nil将图像更改为点
我需要使用自定义图像而不是普通点来实现UIPageControl 。 所以我创建了一个自定义类并通过故事板连接它。 从ios7开始，UIPageControl的子视图包含UIView而不是UIImageView 。 生成的UIView （ UIIpageControl子视图）的子视图不包含任何子视图，因此我收到错误：
致命错误：在展开Optional值时意外发现nil 。
我可能错在哪里？
class WhitePageControl:UIPageControl{ let activeImage = UIImage(named: "dot_white") let inactiveImage = UIImage(named: "dot_white_e") override init(frame: CGRect){ super.init(frame: frame) } required init(coder aDecoder: NSCoder){ super.init(coder: aDecoder) } func updateDots(){ println(self.subviews.count) // 3 println(self.numberOfPages) // 3 for var index = 0; index < self.subviews.count; index++ { println(index) var dot:UIImageView! var dotView:UIView = self.subviews[index] as UIView println("1") for subview in dotView.subviews{ // NIL HERE println("2") if subview.isKindOfClass(UIImageView){ println("3") dot = subview as UIImageView if index == self.currentPage{ dot.image = activeImage } else{ dot.image = inactiveImage } } } } } func setCurrentPage(value:Int){ super.currentPage = value self.updateDots() } }
这是我的解决方案：
import Foundation class PageControl: UIPageControl { var activeImage: UIImage! var inactiveImage: UIImage! override var currentPage: Int { //willSet { didSet { //so updates will take place after page changed 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 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) } }
将setCurrentPage更改为Current Page，bcoz表示一个是Obj C属性
func currentPage(page: Int) { super.currentPage = page self.updateDots() }
尝试这个。