Delete border of UIView when app changes size class - ios

Question

I have a blue view with a white dashed border. As you can see from the image below, once the app is rotated the view changes its dimensions and the border doesn't adjust to the view's new width and height.
I need to find a way to
Know when the view controller changes its size - perhaps using viewWillTransitionToSize.
Delete the previously drawn border, if any.
Add a new border to the view - in the view's drawRect method.
How can I delete the border previously drawn on the view?
#IBOutlet weak var myView: UIView!
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
coordinator.animateAlongsideTransition(nil, completion: {
_ in
self.myView.setNeedsDisplay()
})
}
class RenderView: UIView {
override func drawRect(rect: CGRect) {
self.addDashedBorder()
}
}
extension UIView {
func addDashedBorder() {
let color = UIColor.whiteColor().CGColor
let shapeLayer:CAShapeLayer = CAShapeLayer()
let frameSize = self.frame.size
let shapeRect = CGRect(x: 0, y: 0, width: frameSize.width, height: frameSize.height)
shapeLayer.bounds = shapeRect
shapeLayer.position = CGPoint(x: frameSize.width/2, y: frameSize.height/2)
shapeLayer.fillColor = UIColor.clearColor().CGColor
shapeLayer.strokeColor = color
shapeLayer.lineWidth = 6
shapeLayer.lineJoin = kCALineJoinRound
shapeLayer.lineDashPattern = [6,3]
shapeLayer.path = UIBezierPath(roundedRect: shapeRect, cornerRadius: 5).CGPath
self.layer.addSublayer(shapeLayer)
}
}
Download sample project here.

Answer 1

This is not the right way to do things. Each time your RenderView is redrawn, its drawRect method will be called, and addDashedBorder will add a new layer to your view.
drawRect is for drawing inside of your view using CoreGraphics or UIKit, not CoreAnimation. Inside that method, you should just draw, nothing else. If you want to use it a layer, layoutSubviews is a better place to add it, and to update it to match the view.
Here are two ways to solve your problem. Both update the border correctly, and animate the border smoothly when the device is rotated.
Alternative 1: Just draw the border in drawRect, rather than using a separate shape layer. Also, set your view's contentMode so it automatically redraws when its size changes.
class ViewController: UIViewController {
#IBOutlet weak var myView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
self.myView.contentMode = .Redraw
}
}
class RenderView: UIView {
override func drawRect(rect: CGRect) {
let path = UIBezierPath(roundedRect: self.bounds, cornerRadius: 5)
path.lineWidth = 6
let pattern: [CGFloat] = [6.0, 3.0]
path.setLineDash(pattern, count: 2, phase: 0)
UIColor.whiteColor().setStroke()
path.stroke()
}
}
Alternative 2: Continue to use CAShapeLayer, but only create a single one, by using a lazy stored property. Update the layer in an override of layoutSubviews, and if necessary, animate it alongside any changes in the view's bounds.
class ViewController: UIViewController {
#IBOutlet weak var myView: UIView!
}
class RenderView: UIView {
// Create the borderLayer, and add it to our view's layer, on demand, only once.
lazy var borderLayer: CAShapeLayer = {
let shapeLayer = CAShapeLayer()
shapeLayer.fillColor = nil
shapeLayer.strokeColor = UIColor.whiteColor().CGColor
shapeLayer.lineWidth = 6
shapeLayer.lineDashPattern = [6,3]
self.layer.addSublayer(shapeLayer)
return shapeLayer
}()
override func layoutSubviews() {
super.layoutSubviews()
// We will update the borderLayer's path to match the view's current bounds.
let newPath = UIBezierPath(roundedRect: self.bounds, cornerRadius: 5).CGPath
// We may be animating from the old bounds to the new bounds.
// If so, we want the borderLayer to animate alongside that.
// (UIView does not do this automatically, since it does not know
// anything about our borderLayer; it's at the the CoreAnimation level,
// below UIKit.)
//
// We want an animation that uses the same properties as the existing
// animation, but applies to a different value: the borderLayer's path.
// We'll find the existing animation on the view's bounds.size,
// and if it exists, add our own animation based on it that will
// apply the path change.
if let viewBoundsAnimation = self.layer.animationForKey("bounds.size") {
let pathAnimation = CABasicAnimation()
pathAnimation.beginTime = viewBoundsAnimation.beginTime
pathAnimation.duration = viewBoundsAnimation.duration
pathAnimation.speed = viewBoundsAnimation.speed
pathAnimation.timeOffset = viewBoundsAnimation.timeOffset
pathAnimation.timingFunction = viewBoundsAnimation.timingFunction
pathAnimation.keyPath = "path"
pathAnimation.fromValue = borderLayer.path
pathAnimation.toValue = newPath
borderLayer.addAnimation(pathAnimation, forKey: "path")
}
// Finally, whether we are animating or not, make the border layer show the new path.
// If we are animating, this will appear when the animation is finished.
// If we are not animating, this will appear immediately.
self.borderLayer.path = newPath
}
}
Note that neither of these alternatives require overriding viewWillTransitionToSize or traitCollectionDidChange. Those are higher-level UIViewController concepts, that may get called during device rotation, but won't happen if some other code changes your view's size. It's better to use the simple UIView-level drawRect or layoutSubviews methods, because they will always work.

Answer 2

Call set needs display when the view transitions.You can detect it by using this function.It works perfectly to detect orientation change
override func traitCollectionDidChange(previousTraitCollection: UITraitCollection?) {
self.myView.setNeedsDisplay()
}