How to zoom in/out an UIImage object when user pinches screen?

Question

I would like to zoom in/out an UIImage object when the user performs the standard pinch action on my application. I'm currently using a UIImageView to display my image, if that detail helps in any way.

I'm trying to figure out how to do this, but no such luck so far.

Any clues?

Answer 1

As others described, the easiest solution is to put your UIImageView into a UIScrollView. I did this in the Interface Builder .xib file.

In viewDidLoad, set the following variables. Set your controller to be a UIScrollViewDelegate.

- (void)viewDidLoad {     [super viewDidLoad];     self.scrollView.minimumZoomScale = 0.5;     self.scrollView.maximumZoomScale = 6.0;     self.scrollView.contentSize = self.imageView.frame.size;     self.scrollView.delegate = self; } 

You are required to implement the following method to return the imageView you want to zoom.

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {     return self.imageView; } 

In versions prior to iOS9, you may also need to add this empty delegate method:

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale { } 

The Apple Documentation does a good job of describing how to do this: