Question

I have one view controller in which I have added UIScrollView & UIImageView programatically. I have added UIPichGestureRecognizer to the UIImageView. My UIImageView is added to UIScrollView as a subview.

My problem is when I try to pinch the image , it zoom in. But when I release the touches from screen it again come to its default size. I can not find the error in code. Please help me.
Below is my code

 - (void)createUserInterface {

    scrollViewForImage = [[UIScrollView alloc]initWithFrame:CGRectMake(20.0f, 60.0f, 280.0f, 200.0f)];
    scrollViewForImage.userInteractionEnabled = YES;
    scrollViewForImage.multipleTouchEnabled = YES;
    scrollViewForImage.backgroundColor = [UIColor redColor];
    scrollViewForImage.autoresizesSubviews = YES;
    scrollViewForImage.maximumZoomScale = 1;
    scrollViewForImage.minimumZoomScale = .50;
    scrollViewForImage.clipsToBounds = YES;
    scrollViewForImage.delegate = self;
    scrollViewForImage.bouncesZoom = YES;
    scrollViewForImage.contentMode = UIViewContentModeScaleToFill;
    [self.contentView addSubview:scrollViewForImage];

    imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0.0f, 0.0f, 280.0f, 200.0f)];
    [imageView setBackgroundColor:[UIColor clearColor]];
    imageView.userInteractionEnabled = YES;
    imageView.multipleTouchEnabled = YES;

    UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinch:)];
        [pinchRecognizer setDelegate:self];
        [imageView addGestureRecognizer:pinchRecognizer];
    //[self.contentView addSubview:imageView];
    [self.scrollViewForImage addSubview:imageView];

    scrollViewForImage.contentSize = CGSizeMake(imageView.frame.size.width , imageView.frame.size.height);

}


-(UIView *) viewForZoomingInScrollView:(UIScrollView *)inScroll {
    return imageView;
}

-(void)pinch:(id)sender {

    [self.view bringSubviewToFront:[(UIPinchGestureRecognizer*)sender view]];

    if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {

        lastScale = 1.0;
        return;
    }

    CGFloat scale = 1.0 - (lastScale - [(UIPinchGestureRecognizer*)sender scale]);
    CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;
    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);
    [[(UIPinchGestureRecognizer*)sender view] setTransform:newTransform];
    lastScale = [(UIPinchGestureRecognizer*)sender scale];
}

Answer 1

From what I can see the problem lies here:

scrollViewForImage.maximumZoomScale = 1;

You are setting the maximum zoom scale of the image to 1 x its full size. This means once you finish pinching the image, it will scale back to 1 x its size.

If you want to be able to zoom the image to a larger size, try settings this value to be higher than 1. e.g.

scrollViewForImage.maximumZoomScale = 3;