ios - Scrollview 只缩放到左上角

Question

我以编程方式创建了一个 ScrollView ，并添加了一个图像作为它的 subview ，但是当我尝试放大图像时，它只会放大到上角，并且不允许我滚动查看图像的不同部分。

这是我用来创建 ScrollView 的代码:

let scrollView = UIScrollView()

var image: NSData!

override func viewDidLoad() {
    super.viewDidLoad()

    scrollView.minimumZoomScale = 1.0
    scrollView.maximumZoomScale = 3.0
    scrollView.zoomScale = 1.0
    scrollView.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height)
    scrollView.delegate = self
    scrollView.isPagingEnabled = false
    scrollView.contentSize = CGSize(width: self.view.frame.width, height: self.view.frame.height)

    view.addSubview(scrollView)

    scrollView.addSubview(imageView)

    imageView.image = UIImage(data: image as Data)
    imageView.contentMode = .scaleAspectFit
    imageView.isUserInteractionEnabled = true

    let longPress = UILongPressGestureRecognizer(target: self, action: #selector(share))
    longPress.minimumPressDuration = 0.5
    longPress.numberOfTapsRequired = 0
    imageView.addGestureRecognizer(longPress)

    let doubleTap = UITapGestureRecognizer(target: self, action: #selector(handleDoubleTap(recognizer:)))
    doubleTap.numberOfTapsRequired = 2
    scrollView.addGestureRecognizer(doubleTap)

}

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

func share(sender: UILongPressGestureRecognizer) {
    if sender.state == .ended {
        if UIImage(data: image as Data) != nil {
            let Item = UIImage(data: self.image! as Data)
            let activity = UIActivityViewController(activityItems: [Item!], applicationActivities: nil)
            activity.excludedActivityTypes = [UIActivityType.print, UIActivityType.addToReadingList, UIActivityType.openInIBooks]
            self.present(activity, animated: true, completion: nil)
        }
    }
}

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

非常感谢您的帮助

Answer 1

当您设置 ScrollView 的缩放比例时，问题出在您的代码中。你没有指定它应该缩放到哪里。很自然地，它会缩放并停留在左上角。

您需要在 handleDoubleTap(recognizer: UITapGestureRecognizer) 中获取触摸的位置，计算缩放的矩形，然后调用 scrollRectToVisible在你的 ScrollView 上。