Question

i am trying to scale in and out a UIButton in the main view, when i press a action button at first, the button zooms in and when i press it again it zooms out but when i press it again to zoom in.. nothing happens.. here is my code:

THE METHODS TO ZOOM IN AND ZOOM OUT ARE IN A OBJECTIVE-C CATEGORY ON UIVIEW

- (void)viewDidLoad
[super viewDidLoad];

//this button is being added in the storyboard
[self.viewToZoom removeFromSuperview];

}

- (IBAction)zoomButton:(id)sender {

if (isShown) {
    [self.view removeSubviewWithZoomOutAnimation:self.viewToZoom duration:1.0 option:0];
    isShown = NO;
} else {
    [self.view addSubviewWithZoomInAnimation:self.viewToZoom duration:1.0 option:0];
    isShown = YES;
}

}

UIView+Animation.m


- (void) addSubviewWithZoomInAnimation:(UIView*)view duration:(float)secs option:(UIViewAnimationOptions)option {

CGAffineTransform trans = CGAffineTransformScale(view.transform, 0.01, 0.01);

view.transform = trans; // do it instantly, no animation
[self addSubview:view];
// now return the view to normal dimension, animating this tranformation
[UIView animateWithDuration:secs delay:0.0 options:option
                 animations:^{
                     view.transform = CGAffineTransformScale(view.transform, 100.0, 100.0);
                 }
                 completion:^(BOOL finished) {
                     NSLog(@"done");
                 } ];   
}


- (void) removeSubviewWithZoomOutAnimation:(UIView*)view duration:(float)secs option:(UIViewAnimationOptions)option {

// now return the view to normal dimension, animating this tranformation
[UIView animateWithDuration:secs delay:0.0 options:option
                 animations:^{
                     view.transform = CGAffineTransformScale(view.transform, 0.01, 0.01);

                 }
                 completion:^(BOOL finished) {
                     [view removeFromSuperview];
                 }];    
}

Thanks,
Newton

Answer 1

Newton, when removeSubviewWithZoomOutAnimation ends the view.transform is an affine transform that scaled the view’s original size down to 0.01. The problem is that when you call addSubviewWithZoomInAnimation the second time you’re again scaling down by 0.01, but now the view.transform will be scaled down to 0.0001, which is not what you’re looking for.

Simply add view.transform = CGAffineTransformIdentity; at the beginning of both animations like this:

- (void) addSubviewWithZoomInAnimation:(UIView*)view duration:(float)secs option:(UIViewAnimationOptions)option {
    view.transform = CGAffineTransformIdentity; 
    CGAffineTransform trans = CGAffineTransformScale(view.transform, 0.01, 0.01);

    view.transform = trans; // do it instantly, no animation
    [self addSubview:view];
    // now return the view to normal dimension, animating this tranformation
    [UIView animateWithDuration:secs delay:0.0 options:option
                     animations:^{
                         view.transform = CGAffineTransformScale(view.transform, 100.0, 100.0);
                     }
                     completion:^(BOOL finished) {
                         NSLog(@"done");
                     } ];   
}


- (void) removeSubviewWithZoomOutAnimation:(UIView*)view duration:(float)secs option:(UIViewAnimationOptions)option {
    view.transform = CGAffineTransformIdentity;
    // now return the view to normal dimension, animating this tranformation
    [UIView animateWithDuration:secs delay:0.0 options:option
                     animations:^{

                         view.transform = CGAffineTransformScale(view.transform, 0.01, 0.01);

                     }
                     completion:^(BOOL finished) {

                         [view removeFromSuperview];
                     }];    
}

I also suggest you to pass the UIViewAnimationOptionBeginFromCurrentState UIViewAnimationOptions which improves the animation result when quickly zooming in and out.

Hope this helps!