How should I keep zoom scale on PinchGestureRecognizer? - ios

Question

I want to make zoom function by PinchGestureRecognizer.
I can scale by this code,but imageView is restored whenever I pinch out.
I want to make the function that If I scale imageView sometimes,it isn't restored every time.
And the code scrollView.minimumZoomScale = 3.0,scrollView.maximumZoomScale = 6.0 don't work.
What should I do?
Here is my code
scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
scrollView.frame = self.view.bounds;
scrollView.backgroundColor = [UIColor blueColor];
scrollView.contentSize = CGSizeMake(imgView.bounds.size.width+100, imgView.bounds.size.height);
scrollView.frame = CGRectMake(0,50,320,500);
scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
scrollView.pagingEnabled = YES;
scrollView.bouncesZoom = YES;
scrollView.minimumZoomScale = 3.0;
scrollView.maximumZoomScale = 6.0;
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
[self.view addSubview:scrollView];
UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc]
initWithTarget:self action:#selector(handlePinchGesture:)];
[scrollView addGestureRecognizer:pinchGesture];
img =[UIImage imageNamed:[NSString stringWithFormat:#"a.jpg"]];
imgView = [[UIImageView alloc]initWithImage:img];
imgView.frame = CGRectMake(0,0, self.view.frame.size.width, 448);
imgView.userInteractionEnabled = YES;
[scrollView imgView];
- (void)handlePinchGesture:(UIPinchGestureRecognizer *)sender {
CGFloat factor = [(UIPinchGestureRecognizer *)sender scale];
imgView.transform = CGAffineTransformMakeScale(factor, factor);
NSLog(#"factor %f",factor);
}

Answer 1

try use CGAffineTransformScale instead like:
imgView.transform = CGAffineTransformScale(imgView.transform, factor, factor);

Answer 2

Try This Code
UIScrollView *scrollview =[[UIScrollView alloc]initWithFrame:CGRectMake(0,0,320,imageViewHeight)];
scrollview.showsVerticalScrollIndicator=YES;
scrollview.scrollEnabled=YES;
scrollview.maximumZoomScale = 3.0;
scrollview.delegate = self;
scrollview.userInteractionEnabled=YES;
[self.view addSubview:scrollview];`

Answer 3

NOTE: this is just the another way to achieve your requirement
one thing if u are using UIScrollView there is no need to add UIPinchGestureRecognizer to scroll view by default it has pinch gesture.
for zooming there is a delegate methods need to override
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
and
- (CGRect)zoomRectForScrollView:(UIScrollView *)scrollView withScale:(float)scale withCenter:(CGPoint)center
for example
//initilization
scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
scrollView.frame = self.view.bounds;
scrollView.backgroundColor = [UIColor blueColor];
scrollView.contentSize = CGSizeMake(imgView.bounds.size.width+100, imgView.bounds.size.height);
scrollView.frame = CGRectMake(0,50,320,500);
scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
scrollView.pagingEnabled = YES;
scrollView.bouncesZoom = YES;
scrollView.minimumZoomScale = 3.0;
scrollView.maximumZoomScale = 6.0;
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.delegate = self; /* add this line */
[self.view addSubview:scrollView];
//this view will be scaled accordingly
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return imgView; //return the view which is the subview of scroll view need to be zoomed
}
//it is the rect for the scaling
- (CGRect)zoomRectForScrollView:(UIScrollView *)scrollView withScale:(float)scale withCenter:(CGPoint)center
{
CGRect zoomRect;
zoomRect.size.height = scrollView.frame.size.height / scale;
zoomRect.size.width = scrollView.frame.size.width / scale;
zoomRect.origin.x = center.x - (zoomRect.size.width / 2.0);
zoomRect.origin.y = center.y - (zoomRect.size.height / 2.0);
return zoomRect;
}