ios - 当 UIScrollView 在 ViewController 上显示时 UIButton 不显示

Question

我有一个 UIViewController 附加到一个类，下面是 Swift 代码。这段代码主要是向 View Controller 添加了一个带有图像的 UIScrollView。

我想添加一个 UIButton 到 ViewController 我可以通过代码来完成，但是在这种情况下，我想添加 UIButton 到 ViewController 使用 Storyboard。

当我添加一个 UIButton 然后运行我的项目时，UIButton 不可见，只有 UIScrollView 可见。

问题:

这是怎么回事，为什么 UIButton 不可见？当我运行项目时，如何添加一个 UIButton(到 Storyboard)并确保它可见并位于 UIScrollView(以编程方式创建)的前面？

---

class ScrollViewController: UIViewController, UIScrollViewDelegate {
    var scrollView: UIScrollView!
    var imageView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        imageView = UIImageView(image: UIImage(named: "image.png"))

        scrollView = UIScrollView(frame: view.bounds)
        scrollView.backgroundColor = UIColor.blackColor()
        scrollView.contentSize = imageView.bounds.size
        scrollView.autoresizingMask = [UIViewAutoresizing.FlexibleWidth, UIViewAutoresizing.FlexibleHeight]

        scrollView.contentOffset = CGPoint(x: 1000, y: 450)

        scrollView.addSubview(imageView)
        view.addSubview(scrollView)

        scrollView.delegate = self
        setZoomScale()
        setupGestureRecognizer()
    }

    func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        return imageView
    }

    override func viewWillLayoutSubviews() {
        setZoomScale()
    }

    func setZoomScale() {
        let imageViewSize = imageView.bounds.size
        let scrollViewSize = scrollView.bounds.size
        let widthScale = scrollViewSize.width / imageViewSize.width
        let heightScale = scrollViewSize.height / imageViewSize.height

        scrollView.minimumZoomScale = min(widthScale, heightScale)
        scrollView.zoomScale = 1.0
    }

    func scrollViewDidZoom(scrollView: UIScrollView) {
        let imageViewSize = imageView.frame.size
        let scrollViewSize = scrollView.bounds.size
        let verticalPadding = imageViewSize.height < scrollViewSize.height ? (scrollViewSize.height - imageViewSize.height) / 2 : 0
        let horizontalPadding = imageViewSize.width < scrollViewSize.width ? (scrollViewSize.width - imageViewSize.width) / 2 : 0

        scrollView.contentInset = UIEdgeInsets(top: verticalPadding, left: horizontalPadding, bottom: verticalPadding, right: horizontalPadding)
    }

    func setupGestureRecognizer() {
        let doubleTap = UITapGestureRecognizer(target: self, action: "handleDoubleTap:")
        doubleTap.numberOfTapsRequired = 2
        scrollView.addGestureRecognizer(doubleTap)
    }

    func handleDoubleTap(recognizer: UITapGestureRecognizer) {
        if (scrollView.zoomScale > scrollView.minimumZoomScale) {
            scrollView.setZoomScale(scrollView.minimumZoomScale, animated: true)
        } else {
            scrollView.setZoomScale(scrollView.maximumZoomScale, animated: true)
        }
    }
}

Answer 1

您的 ScrollView 在 z 轴上阻挡了 UIButton，请使用

- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;

在 UIButton 下方插入 ScrollView

swift :

func insertSubview(view: UIView, atIndex index: Int) {
}

回答:

而不是这一行view.addSubview(scrollView)，你需要做self.view.insertSubview(scrollView, atIndex: 0)并确保 UIButton 位于 scrollView 之上。