ios - 滚动期间崩溃，因为边界返回为零

Question

我的应用程序崩溃并显示此消息:

'CALayerInvalidGeometry', reason: 'CALayer position contains NaN: [nan nan]'

这是因为我的缩放比例计算为无穷大(除以零)

我正在尝试不使用 Storyboards - 所以一切都是以编程方式完成的。我有两个 ViewController 的。源 ViewController 将新的 ViewController 推送到堆栈上，如下所示:

..
let destinationVC  = DetailViewController()
destinationVC.setWith(img: photo)
navigationController?.pushViewController(destinationVC, animated: true)
...

现在，当我缩小 scrollView 时，我的 destinationVC 崩溃了。这是因为在 updateMinZoomScaleForSize 中，bounds 返回 0。我试过在其他几个地方调用这个函数:

1. viewDidLayoutSubviews - 仍然崩溃
2. viewWillLayoutSubviews - 仍然崩溃
3. viewWillAppear - 仍然崩溃
4. viewDidAppear - 没有崩溃，但图像“跳”到位

我还尝试在 setWith(img: UIImage) 方法中调用 image.setNeedsDisplay() 和 image.setNeedsLayout 但是我仍然观察到相同的结果。

这是我的destinationVC的完整代码

private let image : UIImageView = {
    let img = UIImageView()
    img.translatesAutoresizingMaskIntoConstraints = false
    img.contentMode = .scaleAspectFit
    return img
}()


private lazy var scrollView : UIScrollView! = {
    let scroll = UIScrollView(frame: view.bounds)
    scroll.contentSize = image.bounds.size
    scroll.translatesAutoresizingMaskIntoConstraints = false
    return scroll
}()

func setWith(img: UIImage) {
    self.image.image = img
    image.setNeedsDisplay()
    image.setNeedsLayout()
    updateMinZoomScaleForSize(view.bounds.size)
}

override func viewDidLoad() {
    super.viewDidLoad()
    self.view.backgroundColor = UIColor.white

    /// Add scrollview
    view.addSubview(scrollView)
    scrollView.addSubview(image)
    scrollView.delegate = self
    addScrollViewConstraints()
    addImageConstraints()
}

private func addScrollViewConstraints() {
    let margins = view.safeAreaLayoutGuide
    scrollView.leftAnchor.constraint(equalTo: margins.leftAnchor).isActive = true
    scrollView.rightAnchor.constraint(equalTo: margins.rightAnchor).isActive = true
    scrollView.topAnchor.constraint(equalTo: margins.topAnchor).isActive = true
    scrollView.bottomAnchor.constraint(equalTo: margins.bottomAnchor).isActive = true


}

private func addImageConstraints() {
    image.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
    image.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
    image.leftAnchor.constraint(equalTo: scrollView.leftAnchor).isActive = true
    image.rightAnchor.constraint(equalTo: scrollView.rightAnchor).isActive = true
}

func viewForZooming(in scrollView: UIScrollView) -> UIView? {
    return image
}

private func updateMinZoomScaleForSize(_ size: CGSize) {
    print(image.bounds.width)
    let widthScale = size.width / image.bounds.width
    let heightScale = size.height / image.bounds.height
    let minScale = min(widthScale, heightScale)

    scrollView.minimumZoomScale = minScale
    scrollView.zoomScale = minScale
}

Answer 1

设置UIImageView 的.image 属性不会改变UIImageView 的框架。

尝试将您的 setWith() 函数更改为:

func setWith(img: UIImage) {
    self.image.image = img
    image.frame.size = img.size
    updateMinZoomScaleForSize(view.bounds.size)
}