Question

I have a UIView class that contains a custom UISlider. When this UIView is added to a viewController it is randomly rotated using

newSlider.transform = CGAffineTransformRotate(newSlider.transform, degreesToRadians(random));

Now what i’m trying to do is animate the UISlider thumb image flying off the end of the slider.
The problem i’m facing is getting the coordinates of the start/end of the slider so I can work out which way the thumb image is travelling.

I have tried using trackRectForBounds but it gives me the exact same coordinates regardless of the rotation applied to the UIView

I have tried these inside my UIView class:

CGRect trackRect = [customSlider trackRectForBounds:customSlider.bounds];

and

CGRect trackRect2 = [customSlider trackRectForBounds:self.window.bounds];

which give me {{2, 1}, {288, 50}} & {{2, 215}, {316, 50}} regardless of rotation. I think it’s giving me the rect from within the UIView and not the screen.

Answer 1

Getting the end-points of slider can be done like this:

CGFloat rotation = [[newSlider.layer valueForKeyPath:@"transform.rotation.z"] floatValue];

CGFloat halfWidth = newSlider.bounds.size.width/2;
CGPoint sliderCenter = newSlider.center;
sliderCenter.y += newSlider.bounds.size.height/2; //this shouldn't be needed but it seems it is

CGFloat x1 = sliderCenter.x - halfWidth * cos(rotation);
CGFloat x2 = sliderCenter.x + halfWidth * cos(rotation);

CGFloat y1 = sliderCenter.y - halfWidth * sin(rotation);
CGFloat y2 = sliderCenter.y + halfWidth * sin(rotation);

CGPoint T1 = CGPointMake(x1, y1);
CGPoint T2 = CGPointMake(x2, y2);