Swift - How to create a view with a shape cropped

问题:

I'm trying to achieve the result shown in the image using swift 1.2 and xcode 6.

Basically I want to create a view with a shape cut in it to be able to see the the view below to make a tutorial for my app. I know how to create a circular shape but i don't know how to cut it out in a view. I need a complete example on how to do it please. Thanks in advance

回答1:

The easiest way to do this would be to create a png image with partly transparent white around the outside and a clear circle in the middle. Then stack 2 image views on top of each other, with the masking image on top, and set its "opaque" flag to false.

You could also do this by creating a CAShapeLayer and set it up to use a translucent white color, then install a shape that is the square with the hole cut out of it shape. You'd install that shape layer on top of your image view's layer.

The most general-purpose way to do that would be to create a custom subclass of UIImageView and have the init method of your subclass create and install the shape layer. I just created a gist yesterday that illustrated creating a custom subclass of UIImageView. Here is the link: ImageViewWithGradient gist

That gist creates a gradient layer. It would be a simple matter to adapt it to create a shape layer instead, and if you modified the layoutSubviews method you could make it adapt the view and path if the image view gets resized.

EDIT:

Ok, I took the extra step of creating a playground that creates a cropping image view. You can find that at ImageViewWithMask on github

The resulting image for my playground looks like this:

回答2:

Even though there is an answer, i'd like to share my way:

// Let's say that you have an outlet to the image view called imageView
// Create the white view 
let whiteView = UIView(frame: imageView.bounds) 
let maskLayer = CAShapeLayer() //create the mask layer

// Set the radius to 1/3 of the screen width
let radius : CGFloat = imageView.bounds.width/3 

// Create a path with the rectangle in it.
let path = UIBezierPath(rect: imageView.bounds)
// Put a circle path in the middle
path.addArcWithCenter(imageView.center, radius: radius, startAngle: 0.0, endAngle: CGFloat(2*M_PI), clockwise: true)

// Give the mask layer the path you just draw
maskLayer.path = path.CGPath
// Fill rule set to exclude intersected paths
maskLayer.fillRule = kCAFillRuleEvenOdd

// By now the mask is a rectangle with a circle cut out of it. Set the mask to the view and clip.
whiteView.layer.mask = maskLayer
whiteView.clipsToBounds = true

whiteView.alpha = 0.8
whiteView.backgroundColor = UIColor.whiteColor()

//If you are in a VC add to the VC's view (over the image)
view.addSubview(whiteView)    
// Annnnnd you're done.

回答3:

Here is sample code for how you can make a circle Mask for a UIView:

let sampleView = UIView(frame: UIScreen.mainScreen().bounds)
let maskLayer = CALayer()
maskLayer.frame = sampleView.bounds
let circleLayer = CAShapeLayer()
//assume the circle's radius is 100
circleLayer.frame = CGRectMake(sampleView.center.x - 100, sampleView.center.y - 100, 200, 200)
let circlePath = UIBezierPath(ovalInRect: CGRectMake(0, 0, 200, 200))
circleLayer.path = circlePath.CGPath
circleLayer.fillColor = UIColor.blackColor().CGColor
maskLayer.addSublayer(circleLayer)

sampleView.layer.mask = maskLayer

Here is what I made in the playground:

回答4:

    //assume you create a UIImageView and content image before execute this code
  let sampleMask = UIView()
    sampleMask.frame = self.view.frame
    sampleMask.backgroundColor =  UIColor.black.withAlphaComponent(0.6)
    //assume you work in UIViewcontroller
    self.view.addSubview(sampleMask)
    let maskLayer = CALayer()
    maskLayer.frame = sampleMask.bounds
    let circleLayer = CAShapeLayer()
    //assume the circle's radius is 150
    circleLayer.frame = CGRect(x:0 , y:0,width: sampleMask.frame.size.width,height: sampleMask.frame.size.height)
    let finalPath = UIBezierPath(roundedRect: CGRect(x:0 , y:0,width: sampleMask.frame.size.width,height: sampleMask.frame.size.height), cornerRadius: 0)
    let circlePath = UIBezierPath(ovalIn: CGRect(x:sampleMask.center.x - 150, y:sampleMask.center.y - 150, width: 300, height: 300))
    finalPath.append(circlePath.reversing())
    circleLayer.path = finalPath.cgPath
    circleLayer.borderColor = UIColor.white.withAlphaComponent(1).cgColor
     circleLayer.borderWidth = 1
    maskLayer.addSublayer(circleLayer)

    sampleMask.layer.mask = maskLayer

回答5:

class MakeTransparentHoleOnOverlayView: UIView {

    @IBOutlet weak var transparentHoleView: UIView!

    // MARK: - Drawing

    override func draw(_ rect: CGRect) {
        super.draw(rect)

        if self.transparentHoleView != nil {
            // Ensures to use the current background color to set the filling color
            self.backgroundColor?.setFill()
            UIRectFill(rect)

            let layer = CAShapeLayer()
            let path = CGMutablePath()

            // Make hole in view's overlay
            // NOTE: Here, instead of using the transparentHoleView UIView we could use a specific CFRect location instead...
            path.addRect(transparentHoleView.frame)
            path.addRect(bounds)

            layer.path = path
            layer.fillRule = kCAFillRuleEvenOdd
            self.layer.mask = layer
        }
    }

    override func layoutSubviews () {
        super.layoutSubviews()
    }

    // MARK: - Initialization

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }
}