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I'm new to iOS and I've been stuck for a while on this. My goal is to programmatically zoom to a specific spot when the user pinches anywhere in the view. This may seem strange, but it's an internal app not for the App Store. Right now, when I pinch to zoom, nothing happens.

On my View (it's a single view application), I have images that I'd like to zoom in on programmatically. Here's what I have done.

  1. In the Interface Builder, I dragged a Scroll View object onto my View, and changed the size to fit the View

  2. In the Scroll View, I set the minimum zoom = 0 and the maximum zoom = 1000 (just to make sure this wasn't the problem)

  3. I dragged a Pinch Gesture Recognizer on top of the UIScrollView.

  4. I right-clicked the UIGestureRecognizer, and created an action called handlePinch() where I placed my code to programmatically zoom when the pinch was recognized.

  5. Implemented the zoom in handlePinch (shown below)

    - (IBAction)handlePinch:(UIPinchGestureRecognizer *)sender {
    CGRect zoomRect;

    zoomRect.origin.x = 500;
    zoomRect.origin.y = 500;
    zoomRect.size.width = 512;
    zoomRect.size.height = 384;

    [scrollView zoomToRect:zoomRect animated:YES ];
  }

Known: - The pinch gesture is being recognized, and handlePinch is being called

Thank you for any answers or suggestions in advance!

corbin
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  • is the scroll view content (i.e, its top level subview) larger than the scroll view frame? – sergio Feb 04 '13 at 22:24
  • Actually both of my images were larger than the main View and larger than the UIScrollView as well. I've made the images smaller than the View and UIScrollView, but still nothing happens on the pinch gesture. I've also tried embedding the image view in the main view and the UIScrollView. – corbin Feb 05 '13 at 01:29

1 Answers1

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You don't need a pinch gesture to do this, since the zooming is built in. Here's what to do.

In your view controller header file, add the scroll view delegate:

@interface MyViewController : UIViewController <UIScrollViewDelegate>

Next in the implementation file, preferably in your viewDidLoad, set the scroll view's delegate to self:

- (void)viewDidLoad {
    //other stuff
    self.scrollView.delegate = self;
}

Then, copy and paste this scroll view delegate method into your implementation file:

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    if (scrollView == self.scrollView) {
        return self.viewToBeZoomed;
    }
}

self.viewToBeZoomed is the view you want to zoom. This view is a subview of self.scrollView.

Jeffrey Sun
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