如何在UIScrollView中启用放大

Question

如何在UIScrollView中启用缩放效果？

Answer 1

答案在这里:

滚动视图还处理内容的缩放和平移.当用户进行捏合或捏合手势时,滚动视图调整内容的偏移和缩放.当手势结束时,管理内容视图的对象应该根据需要更新内容的子视图.(请注意,手势可能会结束,手指仍然可能已关闭.)当手势正在进行时,滚动视图不会向子视图发送任何跟踪调用.

UIScrollView类可以有一个必须采用UIScrollViewDelegate协议的委托.要使缩放和平移工作,委托必须实现viewForZoomingInScrollView:和scrollViewDidEndZooming:withView:atScale:; 此外,最大(maximumZoomScale)和最小(minimumZoomScale)缩放比例必须不同.

所以:

1. 您需要一个在您的实例上实现UIScrollViewDelegate并设置的委托delegateUIScrollView
2. 在您的代理,你必须实现一个方法:viewForZoomingInScrollView:(必须返回内容查看你感兴趣的缩放).您也可以选择实施scrollViewDidEndZooming:withView:atScale:.
3. 在您的UIScrollView实例上,您必须设置minimumZoomScale和maximumZoomScale不同(默认情况下它们是1.0).

注意:有趣的是,如果你想打破缩放的话.nil在viewForZooming...方法中返回是否足够？它确实打破了缩放,但是一些手势将被搞砸(两个手指).因此,要打破缩放,您应将最小和最大缩放比例设置为1.0.

Answer 2

阅读这篇Ray Wenderlich教程:

http://www.raywenderlich.com/76436/use-uiscrollview-scroll-zoom-content-swift

如果您按照"滚动和缩放较大图像"部分进行操作,它将获得图像并使您能够进行捏合和缩放.

如果链接被更改,这里是主要信息:将此代码放在视图控制器中(这将设置主要功能):

override func viewDidLoad() {
  super.viewDidLoad()

  // 1
  let image = UIImage(named: "photo1.png")!
  imageView = UIImageView(image: image)
  imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size:image.size)
  scrollView.addSubview(imageView)

  // 2
  scrollView.contentSize = image.size

  // 3
  var doubleTapRecognizer = UITapGestureRecognizer(target: self, action: "scrollViewDoubleTapped:")
  doubleTapRecognizer.numberOfTapsRequired = 2
  doubleTapRecognizer.numberOfTouchesRequired = 1
  scrollView.addGestureRecognizer(doubleTapRecognizer)

  // 4
  let scrollViewFrame = scrollView.frame
  let scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
  let scaleHeight = scrollViewFrame.size.height / scrollView.contentSize.height
  let minScale = min(scaleWidth, scaleHeight);
  scrollView.minimumZoomScale = minScale;

  // 5
  scrollView.maximumZoomScale = 1.0
  scrollView.zoomScale = minScale;

  // 6
  centerScrollViewContents()
}

将其添加到课程中:

func centerScrollViewContents() {
  let boundsSize = scrollView.bounds.size
  var contentsFrame = imageView.frame

  if contentsFrame.size.width < boundsSize.width {
    contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0
  } else {
    contentsFrame.origin.x = 0.0
  }

  if contentsFrame.size.height < boundsSize.height {
    contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0
  } else {
    contentsFrame.origin.y = 0.0
  }

  imageView.frame = contentsFrame
}

如果你想要识别双击手势,那么这个:

func scrollViewDoubleTapped(recognizer: UITapGestureRecognizer) {
  // 1        
  let pointInView = recognizer.locationInView(imageView)

  // 2
  var newZoomScale = scrollView.zoomScale * 1.5
  newZoomScale = min(newZoomScale, scrollView.maximumZoomScale)

  // 3
  let scrollViewSize = scrollView.bounds.size
  let w = scrollViewSize.width / newZoomScale
  let h = scrollViewSize.height / newZoomScale
  let x = pointInView.x - (w / 2.0)
  let y = pointInView.y - (h / 2.0)

  let rectToZoomTo = CGRectMake(x, y, w, h);

  // 4
  scrollView.zoomToRect(rectToZoomTo, animated: true)
}

如果你想要更多的细节阅读教程,但这几乎涵盖了它.

Answer 3

确保将 viewController 设置为滚动视图委托并实现：

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