Question

I am using the UIPinchGestureRecognizer to expand/reduce a uiview.

UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scaleElement:)];
[pinchGesture setDelegate:self];
[element addGestureRecognizer:pinchGesture];
[pinchGesture release];

//Scale element method

- (void)scaleElement:(UIPinchGestureRecognizer *)gestureRecognizer {
    UIView *element = [gestureRecognizer view];
    [self adjustAnchorPointForGestureRecognizer:gestureRecognizer];
    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan){
        lastTouchPosition = [gestureRecognizer locationInView:element];
    } 
    else if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged){
            CGPoint currentTouchPosition = [gestureRecognizer locationInView:element];
            CGPoint deltaMove = [self calculatePointDistancewithPoint1:currentTouchPosition andPoint2:lastTouchPosition];
            float distance = sqrt(deltaMove.x*deltaMove.x + deltaMove.y*deltaMove.y);
            float hScale = 1 - deltaMove.x/distance * (1-gestureRecognizer.scale);
            float vScale = 1 - deltaMove.y/distance * (1-gestureRecognizer.scale);
            if (distance == 0) {
                hScale = 1;
                vScale = 1;
            }
            element.transform = CGAffineTransformScale([element transform], hScale, vScale);
            CGAffineTransform transform = CGAffineTransformMakeScale(hScale, vScale);
            element.bounds = CGRectApplyAffineTransform(element.bounds, transform);
                [gestureRecognizer setScale:1];
                lastTouchPosition = currentTouchPosition;
            }
            if ([gestureRecognizer state] == UIGestureRecognizerStateEnded) {
                NSLog(@"scaling over");
                NSLog(@"bounds = %@",NSStringFromCGRect(element.bounds));
                NSLog(@"frame = %@", NSStringFromCGRect(element.frame));
            }
            NSLog(@"scalePiece exit");
    }

//adjustAnchorPointForGestureRecognizer method

    - (void)adjustAnchorPointForGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer {
        if (gestureRecognizer.state == UIGestureRecognizerStateBegan) {
            UIView *elementToAdjust = gestureRecognizer.view;
            [self.view bringSubviewToFront:gestureRecognizer.view];
            CGPoint locationInView = [gestureRecognizer locationInView:elementToAdjust];
            CGPoint locationInSuperview = [gestureRecognizer locationInView:elementToAdjust.superview];
            elementToAdjust.layer.anchorPoint = CGPointMake(locationInView.x / elementToAdjust.bounds.size.width, locationInView.y / elementToAdjust.bounds.size.height);
            elementToAdjust.center = locationInSuperview;
        }
    }

Console print:

bounds = {{0, 0}, {178.405, 179.018}}
frame = {{300.642, 566.184}, {192.899, 194.227}}

Why isn’t the bounds adjusting when the frame is changing ?
Does it have anything to do with auto resizing masks as I have subviews to this view ?

Answer 1

This has nothing to do with UIPinchGestureRecognizer. This has everything to do with your setting the transform to perform scaling. Changing the transform does not change bounds. It just changes how this view’s coordinate space (bounds) maps to the superview’s coordinate space (frame). If you need bounds to match frame, you have to change one of them directly, not use transform. That said, you should generally use transform because it’s much faster.

EDIT

If you don’t mean to scale, but rather mean to resize the view, call setBounds:. You can find the new bounds by applying the transform to the bounds rather than the element.

CGPoint currentTouchPosition = [gestureRecognizer locationInView:element];
CGPoint deltaMove = [self calculatePointDistancewithPoint1:currentTouchPosition andPoint2:lastTouchPosition];
...

CGAffineTransform transform = CGAffineTransformMakeScale(hScale, vScale);
self.bounds = CGRectApplyAffineTransform(self.bounds, transform);