UIButton - move and scale - ios

Question

I have an UIButton that I've creates programmatically. Actually it should'n be UIButton, I just need to have possibility to mark some area above the image.
So the features I need it - move object and resize it. For this i have 2 methods:
- (void) objMove:(id) sender withEvent:(UIEvent *) event
{
UIControl *control = sender;
UITouch *t = [[event allTouches] anyObject];
CGPoint pPrev = [t previousLocationInView:control];
CGPoint p = [t locationInView:control];
CGPoint center = control.center;
center.x += p.x - pPrev.x;
center.y += p.y - pPrev.y;
control.center = center;
}
- (void)objScale:(UIPinchGestureRecognizer *)recognizer
{
UIView *pinchView = recognizer.view;
CGRect bounds = pinchView.bounds;
CGPoint pinchCenter = [recognizer locationInView:pinchView];
pinchCenter.x -= CGRectGetMidX(bounds);
pinchCenter.y -= CGRectGetMidY(bounds);
CGAffineTransform transform = pinchView.transform;
transform = CGAffineTransformTranslate(transform, pinchCenter.x, pinchCenter.y);
CGFloat scale = recognizer.scale;
transform = CGAffineTransformScale(transform, scale, scale);
transform = CGAffineTransformTranslate(transform, -pinchCenter.x, -pinchCenter.y);
pinchView.transform = transform;
recognizer.scale = 1.0;
}
Scale works ok. Moving looks ok until I change the size of object - when i increase object it become moves slower than finger, and vice versa - if object smaller than original it moves faster than finger. why it works like this?

Answer 1

I think you should get startPoint and startCenter in
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
// get startPoint and startCenter here
}
- (void) objMove:(id) sender withEvent:(UIEvent *) event
{
UIControl *control = sender;
UITouch *t = [[event allTouches] anyObject];
CGPoint p = [t locationInView:control];
startCenter.x += p.x - startPoint.x;
startCenter.y += p.y - startPoint.y;
control.center = startCenter;
}
Change your code like this, maybe it works.
Your center is current center, p is current point, pPrev is previous point.
current center adds previous point moved size is wrong.
You should get relative distance, not dynamic distance.