问题
I was hoping someone could help me out. I am trying to allow a user to pinch zoom on a UIImageView(with a max and min level allowed). But for some reason the it does not work right. The image zooms a little then just bounces back. Thank you.
here is the zoom func
func zoom(sender:UIPinchGestureRecognizer) {
if sender.state == .Ended || sender.state == .Changed {
let currentScale = self.view.frame.size.width / self.view.bounds.size.width
var newScale = currentScale*sender.scale
if newScale < 1 {
newScale = 1
}
if newScale > 9 {
newScale = 9
}
let transform = CGAffineTransformMakeScale(newScale, newScale)
self.imageView?.transform = transform
sender.scale = 1
}
}
回答1:
UIImageView pinch zoom with UIScrollView || image zooming ios in swift 3 and Xcode 8 letter Youtube video URL
set uiscrollview Delegate in storyboard
class PhotoDetailViewController: UIViewController, UIScrollViewDelegate {
@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var imgPhoto: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
scrollView.minimumZoomScale = 1.0
scrollView.maximumZoomScale = 6.0
// scrollView.delegate = self - it is set on the storyboard.
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imgPhoto
}
回答2:
I decided to add the imageView to a UIScrollView. It allows the user to zoom and pan over. Here is the code I used.
in order to set max/min zoom I used :
scrollImg.minimumZoomScale = 1.0
scrollImg.maximumZoomScale = 10.0
here is the rest of the code.
var vWidth = self.view.frame.width
var vHeight = self.view.frame.height
var scrollImg: UIScrollView = UIScrollView()
scrollImg.delegate = self
scrollImg.frame = CGRectMake(0, 0, vWidth!, vHeight!)
scrollImg.backgroundColor = UIColor(red: 90, green: 90, blue: 90, alpha: 0.90)
scrollImg.alwaysBounceVertical = false
scrollImg.alwaysBounceHorizontal = false
scrollImg.showsVerticalScrollIndicator = true
scrollImg.flashScrollIndicators()
scrollImg.minimumZoomScale = 1.0
scrollImg.maximumZoomScale = 10.0
defaultView!.addSubview(scrollImg)
imageView!.layer.cornerRadius = 11.0
imageView!.clipsToBounds = false
scrollImg.addSubview(imageView!)
I also had to add this as well
func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
return self.imageView
}
Swift 3 & above function prototype
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return self.mainImage
}
回答3:
The option for swift 4
class ViewController: UIViewController, UIScrollViewDelegate {
@IBOutlet weak var scrolView: UIScrollView!
@IBOutlet weak var imgPhoto: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
scrolView.delegate = self
scrolView.minimumZoomScale = 1.0
scrolView.maximumZoomScale = 10.0
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imgPhoto
}
}
回答4:
You can use ImageScrollView open source, a zoomable and scrollable image view. http://github.com/huynguyencong/ImageScrollView
Like this opensource, add ImageView to ScrollView
open class ImageScrollView: UIScrollView {
var zoomView: UIImageView? = nil
}
extension ImageScrollView: UIScrollViewDelegate{
public func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return zoomView
}
public func scrollViewDidZoom(_ scrollView: UIScrollView) {
adjustFrameToCenter()
}
}
回答5:
In my view, the problem is your determination of currentScale. It always equals 1, because you change the scale of your imageView. You should assign your currentScale as follows:
let currentScale = self.imageView?.frame.size.width / self.imageView?.bounds.size.width
回答6:
Swift 3 solution
By default UIImageView's userInteration is disabled. Enable it before adding any gestures in UIImageView.
imgView.isUserInteractionEnabled = true
The scale factor relative to the points of the two touches in screen coordinates
var lastScale:CGFloat!
func zoom(gesture:UIPinchGestureRecognizer) {
if(gesture.state == .began) {
// Reset the last scale, necessary if there are multiple objects with different scales
lastScale = gesture.scale
}
if (gesture.state == .began || gesture.state == .changed) {
let currentScale = gesture.view!.layer.value(forKeyPath:"transform.scale")! as! CGFloat
// Constants to adjust the max/min values of zoom
let kMaxScale:CGFloat = 2.0
let kMinScale:CGFloat = 1.0
var newScale = 1 - (lastScale - gesture.scale)
newScale = min(newScale, kMaxScale / currentScale)
newScale = max(newScale, kMinScale / currentScale)
let transform = (gesture.view?.transform)!.scaledBy(x: newScale, y: newScale);
gesture.view?.transform = transform
lastScale = gesture.scale // Store the previous scale factor for the next pinch gesture call
}
}
回答7:
Using Swift 5.0, here is how it works for me:
let myImageView = UIImageView(image: myImage)
myImageView.isUserInteractionEnabled = true
let pinchMethod = UIPinchGestureRecognizer(target: self, action: #selector(pinchImage(sender:)))
myImageView.addGestureRecognizer(pinchMethod)
@objc func pinchImage(sender: UIPinchGestureRecognizer) {
guard let sender.view != nil else { return }
if let scale = (sender.view?.transform.scaledBy(x: sender.scale, y: sender.scale)) {
guard scale.a > 1.0 else { return }
guard scale.d > 1.0 else { return }
sender.view?.transform = scale
sender.scale = 1.0
}
}
You can use scale.a, scale.b, scale.c, scale.d, scale.tx and scale.ty to set your scale limits.
回答8:
Swift 3 solution
This is the code I used. I added imageView to scrollView as a subview.
class ZoomViewController: UIViewController,UIScrollViewDelegate {
@IBOutlet weak var scrollView:UIScrollView!
@IBOutlet weak var imageView:UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
scrollView.delegate = self
scrollView.minimumZoomScale = 1.0
scrollView.maximumZoomScale = 10.0//maximum zoom scale you want
scrollView.zoomScale = 1.0
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imageView
}
回答9:
Supporting Swift 5.1, You can create an extension of UIImageView, like this:
extension UIImageView {
func enableZoom() {
let pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(startZooming(_:)))
isUserInteractionEnabled = true
addGestureRecognizer(pinchGesture)
}
@objc
private func startZooming(_ sender: UIPinchGestureRecognizer) {
let scaleResult = sender.view?.transform.scaledBy(x: sender.scale, y: sender.scale)
guard let scale = scaleResult, scale.a > 1, scale.d > 1 else { return }
sender.view?.transform = scale
sender.scale = 1
}
}
回答10:
I think the biggest problem is at the end of your func, you have sender.scale = 1. If you remove that line of code, your image shouldn't just bounce back each time.
回答11:
I posted an answer here for zoom functionality with both pinch and double tap in Swift 3. Works perfectly.
回答12:
This is an old question but I don't see any answers that explain what is wrong with the original code.
This line:
let currentScale = self.view.frame.size.width / self.view.bounds.size.width
Is working on the main view rather than the imageView so the scale calculation is always ~1
This simple change makes it behave as expected
let currentScale = sender.view!.frame.size.width / sender.view!.bounds.size.width
by changing self to sender (and forcing view to unwrap) the scale calculation works as expected.
回答13:
I ended up here, probably searching the wrong way.
I was after having my imageView in contentMode = .centre. But I was judging it too zoomed in and I was searching a way to zoom it out. Here's how:
self.imageView.contentScaleFactor = 3
1 is as if you were doing anything. More that 1 zooms out... 3 works for me but you need to test it out.
来源：https://stackoverflow.com/questions/30014241/uiimageview-pinch-zoom-swift