drag & rotate gesture on iPad - iphone

Question

I have a problem, I want to add some gesture to a uibutton for move and rotate it, I use this code
[self.button addTarget:self action:#selector(wasDragged:withEvent:) forControlEvents:UIControlEventTouchDragInside];
UIRotationGestureRecognizer *rotationGesture = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:#selector(handleRotate:)];
[self.button addGestureRecognizer:rotationGesture];
- (void)wasDragged:(UIButton *)button withEvent:(UIEvent *)event
{
// get the touch
UITouch *touch = [[event touchesForView:self.button] anyObject];
// get delta
CGPoint previousLocation = [touch previousLocationInView:self.button];
CGPoint location = [touch locationInView:self.button];
CGFloat delta_x = location.x - previousLocation.x;
CGFloat delta_y = location.y - previousLocation.y;
// move button
self.button.center = CGPointMake(self.button.center.x + delta_x,self.button.center.y + delta_y);
}
- (void)handleRotate:(UIRotationGestureRecognizer *)recognizer {
if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateChanged)
{
recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
[recognizer setRotation:0];
}
}
all work I can rotate the button and move the button, the problem is if I rotate the button and then move it...in this case not work, I can move the button but not where I want...where is the problem?

Answer 1

You are calculating the difference between the position of touches relative to the button. This does not work as expected when the button is rotated. Instead you should try computing it relative to the superview of the button or the window.
Instead of this:
CGPoint previousLocation = [touch previousLocationInView:self.button];
CGPoint location = [touch locationInView:self.button];
You should use this:
CGPoint previousLocation = [touch previousLocationInView:self.button.superview];
CGPoint location = [touch locationInView:self.button.superview];