如何在iOS上进行双击缩放和双指轻点缩小操作？

Question

我正在开发一个应用程序，通过使用UIScrollView展示UIImages的画廊。我的问题是如何实现单击进行缩放，双击进行缩小，在处理UIScrollView时该如何操作。

- Bruno

Answer 1

你需要在你的视图控制器中实现UITapGestureRecognizer - 文档 在这里 -

- (void)viewDidLoad
{
    [super viewDidLoad];       

    // what object is going to handle the gesture when it gets recognised ?
    // the argument for tap is the gesture that caused this message to be sent
    UITapGestureRecognizer *tapOnce = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapOnce:)];
    UITapGestureRecognizer *tapTwice = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapTwice:)];

    // set number of taps required
    tapOnce.numberOfTapsRequired = 1;
    tapTwice.numberOfTapsRequired = 2;

    // stops tapOnce from overriding tapTwice
    [tapOnce requireGestureRecognizerToFail:tapTwice];

    // now add the gesture recogniser to a view 
    // this will be the view that recognises the gesture  
    [self.view addGestureRecognizer:tapOnce];
    [self.view addGestureRecognizer:tapTwice];

}

基本上这段代码的意思是，当在self.view中注册了一个UITapGesture时，方法tapOnce或tapTwice将在self中被调用，具体取决于它是单击还是双击。因此，您需要将这些点击方法添加到您的UIViewController中：

- (void)tapOnce:(UIGestureRecognizer *)gesture
{
    //on a single  tap, call zoomToRect in UIScrollView
    [self.myScrollView zoomToRect:rectToZoomInTo animated:NO];
}
- (void)tapTwice:(UIGestureRecognizer *)gesture
{
    //on a double tap, call zoomToRect in UIScrollView
    [self.myScrollView zoomToRect:rectToZoomOutTo animated:NO];
}

希望有所帮助。

- GWed

---

非常感谢您的答复，我会尽快测试并回报。 - Bruno

Webview能否识别在其内部的链接触摸？ - Codesen

[tapOnce requireGestureRecognizerToFail:tapTwice]; 正是我正在寻找的。谢谢！ - smisiewicz

Answer 2

Swift 4.0 版本可以在双击时实现两倍缩放。

@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var imageView: UIImageView!

在某个地方（通常是在viewDidLoad方法中）：

let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(onDoubleTap(gestureRecognizer:)))
tapRecognizer.numberOfTapsRequired = 2
scrollView.addGestureRecognizer(tapRecognizer)

处理程序：

@objc func onDoubleTap(gestureRecognizer: UITapGestureRecognizer) {
    let scale = min(scrollView.zoomScale * 2, scrollView.maximumZoomScale)
    
    if scale != scrollView.zoomScale {
        let point = gestureRecognizer.location(in: imageView)

        let scrollSize = scrollView.frame.size
        let size = CGSize(width: scrollSize.width / scale,
                          height: scrollSize.height / scale)
        let origin = CGPoint(x: point.x - size.width / 2,
                             y: point.y - size.height / 2)
        scrollView.zoom(to:CGRect(origin: origin, size: size), animated: true)
        print(CGRect(origin: origin, size: size))
    }
}

- Avt

---

在Swift 5/Xcode 12.4中，这仍然以相同的方式工作。要使用双击缩小（并带有动画），您只需将以下内容添加到“else”部分即可：scrollView.setZoomScale(scrollView.minimumZoomScale, animated: true)。 - Neph