UISwipeGestureRecognizer配合UIPageControl实现图片滑动切换不生效问题

现有代码的问题汇总 #

• UIPageControl缺少基础配置：未设置numberOfPages与图片数组长度匹配，也未设置初始currentPage，页面加载时没有给图片控件设置默认显示的第一张图
• 左滑边界逻辑错误：当处于最后一张图继续左滑时，原代码执行pageCtl.currentPage = swipePosition + 1会导致页码超出数组合法范围，且没有同步更新正确的页码
• 滑动切换图片后未同步更新pageCtl.currentPage，导致页码指示器和当前展示的图片不对应
• 若imageNames定义在viewDidLoad内部为局部变量，swiped方法无法访问该数组，会引发运行时崩溃

修正后的完整实现代码 #

// 全局属性定义
var swipePosition = 0
@IBOutlet weak var pageCtl: UIPageControl!
@IBOutlet weak var imageView: UIImageView!
// 图片数组设为全局属性
let imageNames = ["cauliflower", "grapres", "Image", "lily", "mango"]

override func viewDidLoad() {
    super.viewDidLoad()
    
    // 配置PageControl基础参数
    pageCtl.numberOfPages = imageNames.count
    pageCtl.currentPage = 0
    // 设置初始展示的第一张图
    imageView.image = UIImage(named: imageNames[swipePosition])
    
    // 添加滑动手势
    let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(swiped))
    swipeRight.direction = .right
    self.view.addGestureRecognizer(swipeRight)

    let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(swiped))
    swipeLeft.direction = .left
    self.view.addGestureRecognizer(swipeLeft)
}

@objc func swiped(gesture: UIGestureRecognizer) {
    guard let swipeGesture = gesture as? UISwipeGestureRecognizer else { return }
    switch swipeGesture.direction {
    case .left:
        if swipePosition == imageNames.count - 1 {
            // 最后一张左滑回到第一张
            swipePosition = 0
        } else {
            swipePosition += 1
        }
    case .right:
        if swipePosition == 0 {
            // 第一张右滑跳到最后一张
            swipePosition = imageNames.count - 1
        } else {
            swipePosition -= 1
        }
    default:
        break
    }
    // 同步更新图片和页码指示器
    imageView.image = UIImage(named: imageNames[swipePosition])
    pageCtl.currentPage = swipePosition
}

内容的提问来源于stack exchange，提问作者AMIT KUMAR JHAMB