Can't change color of circle drawn in view

问题:

I am trying to update the colour of a circle I have created in a subclass of UIView by creating a method within the class to update the colour as below but the colour does not change.

import UIKit

class badge: UIView {

    struct mine {
        static var p = UIBezierPath(ovalInRect: CGRectMake(0,0,100,100))

}

override func drawRect(rect: CGRect) {
    // Drawing code


    UIColor.blueColor().setFill()
    mine.p.fill()        

}


func colour(whatColour: String) {

    UIColor.redColor().setFill()
    mine.p.fill()
    self.setNeedsDisplay()

}
}

// The above is referenced in view controller with

@IBOutlet weak var myBadge: badge!

// change function colour is called with 

myBadge.colour()

// but the colour of the circle does not change (its still filled in blue)
}

What am I doing wrong?

回答1:

Update: Swift 3 (and Swift 4) syntax:

setNeedsDisplay causes draw to run again, and it sets the fill color back to blue. Try adding a property to your Badge view to store the desiredColour:

class Badge: UIView {

    var desiredColour: UIColor = .blue

    struct mine {
        static var p = UIBezierPath(ovalIn: CGRect(x: 0, y: 0, width: 100, height: 100))
    }

    override func draw(_ rect: CGRect) {
        // Drawing code

        desiredColour.setFill()
        mine.p.fill()
    }

    func colour() {
        desiredColour = .red
        self.setNeedsDisplay()
    }
}

---

If you add didSet to desiredColour, you can have it call setNeedsDisplay for you, and then you don't even need the colour function. So to use it, you just call myBadge.desiredColour = .red and the view will redraw!

class Badge: UIView {

    var desiredColour: UIColor = .blue {
        didSet {
            self.setNeedsDisplay()
        }
    }

    struct mine {
        static var p = UIBezierPath(ovalIn: CGRect(x: 0, y: 0, width: 100, height: 100))
    }

    override func draw(_ rect: CGRect) {
        // Drawing code

        desiredColour.setFill()
        mine.p.fill()
    }
}

---

Here it is running in a Swift Playground: