Specfic part of UIView zoom in/out without increasing hight/width of View objective C iOS

Question

I implement this .but problem is that it increase hight/width of the view with zooming.How to zoom without increasing the hight/width. My UIView hight/width is fixed.My basic aim is that view hight/width remain same but zoom inner side of the view.

    UIPinchGestureRecognizer * pinGeture =  [[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(twoFingerPinch:)];
    [radarViewHolder addGestureRecognizer:pinGeture];



- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer
{
    NSLog(@"Pinch scale: %f", recognizer.scale);

    if([recognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [recognizer scale];
    }

    if ([recognizer state] == UIGestureRecognizerStateBegan ||
        [recognizer state] == UIGestureRecognizerStateChanged) {

        CGFloat currentScale = [[[recognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 -  (lastScale - [recognizer scale]);
        newScale = MIN(newScale, kMaxScale / currentScale);
        newScale = MAX(newScale, kMinScale / currentScale);
        CGAffineTransform transform = CGAffineTransformScale([[recognizer view] transform], newScale, newScale);
        [recognizer view].transform = transform;

        lastScale = [recognizer scale];  // Store the previous scale factor for the next pinch gesture call
    }
}

i read it but this link zoom view with increasing hight/width — Shahbaz Akram, Dec 22 '17 at 07:36

score 2 · Answer 1 · answered Dec 22 '17 at 07:26

Add your view in yourScroll as subView.

[yourScroll addSubView:radarViewHolder];


- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{

    CGFloat size = scrollView.zoomScale;
    if (size > ZoomMaxValue)
    {
        yourScroll.zoomScale = maximumScale;
    }
    if (size > ZoomMinValue && size < ZoomValue && size < 1.01)
    {
        yourScroll.zoomScale = minimumScale;
    }
    ZoomValue = size;
}

score 1 · Accepted Answer · answered Dec 21 '17 at 14:00

1

@ShahbazAkram declare one float variable CGFloat lastScale;

replace this method into your code.

- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer
{
    NSLog(@"Pinch scale: %f", recognizer.scale);

    if([recognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [recognizer scale];
    }

    if ([recognizer state] == UIGestureRecognizerStateBegan ||
        [recognizer state] == UIGestureRecognizerStateChanged) {

        CGFloat currentScale = [[[recognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 -  (lastScale - [recognizer scale]);
        newScale = MIN(newScale, kMaxScale / currentScale);
        newScale = MAX(newScale, kMinScale / currentScale);
        CGAffineTransform transform = CGAffineTransformScale([[recognizer view] transform], newScale, newScale);
        [recognizer view].transform = transform;

        lastScale = [recognizer scale];  // Store the previous scale factor for the next pinch gesture call
    }
}

answered Dec 21 '17 at 14:00

Nirav Kotecha

2,493
1
12
26

1

@ShahbazAkram you can change it max and min scale for zoom as per your requirements. – Nirav Kotecha Dec 21 '17 at 14:01
Yes now zoom work perfectly but problem is that it increase hight / width of the view. But my requirement is that view hight/width remain same but zoom inner side of the view. – Shahbaz Akram Dec 22 '17 at 05:51
1

add gesture in inner side of view – Nirav Kotecha Dec 22 '17 at 05:52
1

You mean i add child view then add gesture on it? – Shahbaz Akram Dec 22 '17 at 05:56
or just show me screenshot that how you want so i can check it – Nirav Kotecha Dec 22 '17 at 05:58
in short, your child view have gesture and superview have `clipsToBound=yes` – Nirav Kotecha Dec 22 '17 at 06:05
1

yes it work perfect can i scroll zooming view to right,left etc. – Shahbaz Akram Dec 22 '17 at 06:24
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/161787/discussion-between-nirav-kotecha-and-shahbaz-akram). – Nirav Kotecha Dec 22 '17 at 06:57

score 0 · Answer 3 · answered Dec 21 '17 at 14:14

When using transform on a view then getter for its frame will multiply its coordinates with this transform. So internally the frame was not really updated.

This is usually not a problem but can be in some cases. In general to avoid such cases all you need to do is add your view to another view and then scale the superview. Assume such code:

let baseView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0))
baseView.backgroundColor = .red
let addedView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0))
addedView.backgroundColor = .green
baseView.addSubview(addedView)
baseView.transform = CGAffineTransform(scaleX: 3.0, y: 3.0)

(Sorry for Swift but it should make no difference for your case)

When printing frames for these 2 views the result is

baseView: (-50 -50; 150 150)
addedView: (0 0; 50 50)

but visually these 2 views are the same and added view overlaps the base view completely.

In your case there is not enough code to show specific fix but if you create a base view for the view you are currently having and scale the base view then your issue with changed frame should be fixed.

Specfic part of UIView zoom in/out without increasing hight/width of View objective C iOS

3 Answers3