iOS Swift Xcode 6: CGAffineTransformRotate with auto-layout anchorpoint - ios

Question

I'm making an app with a rotatable pie chart. However, my pie chart rotates around (0,0) and I can't find a solution to make it rotate around its center.
Some code:
// DRAWING CODE
// Set constants for piePieces
let radius: CGFloat = CGFloat(screen.width * 0.43)
let pi: CGFloat = 3.1415926535
let sliceRad: CGFloat = 2.0 * pi / CGFloat(categoryArray.count)
var currentAngle: CGFloat = -0.5 * sliceRad - 0.5 * pi
let center: CGPoint = CGPoint(x: screen.width / 2.0, y: radius)
println("Center point: \(center)")
//container!.layer.anchorPoint = CGPoint(x: screen.width, y: radius)
// Draw all pie charts, add them to container (chartView)
for category in categoryArray {
let slice = UIView()
slice.frame = self.frame
let shapeLayer = CAShapeLayer()
let scoreIndex = CGFloat(category.calculateScoreIndex())
let sliceRadius: CGFloat = scoreIndex * radius
// Draw the path
var path:UIBezierPath = UIBezierPath()
path.moveToPoint(center)
path.addLineToPoint(CGPoint(x: center.x + sliceRadius * cos(currentAngle), y: center.y + sliceRadius * sin(currentAngle)))
path.addArcWithCenter(center, radius: sliceRadius, startAngle: currentAngle, endAngle: currentAngle + sliceRad, clockwise: true)
path.addLineToPoint(center)
path.closePath()
// For next slice, add 2*pi Rad / n categories
currentAngle += sliceRad
// Add path to shapeLayer
shapeLayer.path = path.CGPath
//shapeLayer.frame = self.frame
shapeLayer.fillColor = SurveyColors().getColor(category.categoryIndex).CGColor
shapeLayer.anchorPoint = center
// Add shapeLayer to sliceView
slice.layer.addSublayer(shapeLayer)
// Add slice to chartView
container!.addSubview(slice)
}
self.addSubview(container!)
//container!.center = center
container!.layer.anchorPoint = center
}
I sheduled a NSTimer to perform a rotation every 2 seconds (for testing purposes):
func rotate() {
let t: CGAffineTransform = CGAffineTransformRotate(container!.transform, -0.78)
container!.transform = t;
}
The pie chart rotates around (0,0). What is going wrong?

Answer 1

I believe a good solution to your problem would be to set a container view:
container = UIView()
container!.frame = CGRect(x: 0.0, y: 0.0, width: screen.width, height: screen.width)
container!.layer.anchorPoint = CGPoint(x: 0.5, y: 0.5)
container!.backgroundColor = UIColor.clearColor()
And then add all slices to this container view:
let slice = UIView()
slice.frame = CGRect(x: 0.0 , y: 0.0 , width: container!.bounds.width, height: container!.bounds.height)
let shapeLayer = CAShapeLayer()
let scoreIndex = CGFloat(category.calculateScoreIndex())
let sliceRadius: CGFloat = scoreIndex * radius
/*
*/
container!.addSubview(slice)
Also, make sure not to add your chart as a subview to a view with auto-layout constraints (which might interfere with you CGAffineTransformRotate).