swift - 只画一半的圆

Question

我只想画圆的左半边或右半边。

我可以毫无问题地绘制从 0 到 0.5(右侧)的圆。但是绘制从 0.5 到 1 的圆圈(左侧)不起作用。

调用:

 addCircleView(circle, isForeground: false, duration: 0.0, fromValue: 0.5,  toValue: 1.0)

这是我的代码:

func addCircleView( myView : UIView, isForeground : Bool, duration : NSTimeInterval, fromValue: CGFloat, toValue : CGFloat ) -> CircleView {
        let circleWidth = CGFloat(280)
        let circleHeight = circleWidth

        // Create a new CircleView
        let circleView = CircleView(frame: CGRectMake(0, 0, circleWidth, circleHeight))

        //Setting the color.
        if (isForeground == true) {

            circleView.setStrokeColor((UIColor(hexString: "#ffefdb")?.CGColor)!)
        } else {
            // circleLayer.strokeColor = UIColor.grayColor().CGColor
            //Chose to use hexes because it's much easier.
            circleView.setStrokeColor((UIColor(hexString: "#51acbc")?.CGColor)!)
        }

        myView.addSubview(circleView)

        //Rotate the circle so it starts from the top.
        circleView.transform = CGAffineTransformMakeRotation(-1.56)

        // Animate the drawing of the circle
        circleView.animateCircleTo(duration, fromValue: fromValue, toValue: toValue)

        return circleView

    }

圆 View 类

import UIKit
extension UIColor {
    /// UIColor(hexString: "#cc0000")
    internal convenience init?(hexString:String) {
        guard hexString.characters[hexString.startIndex] == Character("#") else {
            return nil
        }
        guard hexString.characters.count == "#000000".characters.count else {
            return nil
        }
        let digits = hexString.substringFromIndex(hexString.startIndex.advancedBy(1))
        guard Int(digits,radix:16) != nil else{
            return nil
        }
        let red = digits.substringToIndex(digits.startIndex.advancedBy(2))
        let green = digits.substringWithRange(Range<String.Index>(digits.startIndex.advancedBy(2)..<digits.startIndex.advancedBy(4)))
        let blue = digits.substringWithRange(Range<String.Index>(digits.startIndex.advancedBy(4)..<digits.startIndex.advancedBy(6)))
        let redf = CGFloat(Double(Int(red, radix:16)!) / 255.0)
        let greenf = CGFloat(Double(Int(green, radix:16)!) / 255.0)
        let bluef = CGFloat(Double(Int(blue, radix:16)!) / 255.0)
        self.init(red: redf, green: greenf, blue: bluef, alpha: CGFloat(1.0))
    }
}

class CircleView: UIView {

    var circleLayer: CAShapeLayer!
    var from : CGFloat = 0.0;


    override init(frame: CGRect) {
        super.init(frame: frame)
        self.backgroundColor = UIColor.clearColor()

        // Use UIBezierPath as an easy way to create the CGPath for the layer.
        // The path should be the entire circle.
        let circlePath = UIBezierPath(arcCenter: CGPoint(x: frame.size.width / 2.0, y: frame.size.height / 2.0), radius: (frame.size.width - 10)/2, startAngle: 0.0, endAngle: CGFloat(M_PI * 2.0), clockwise: true)

        // Setup the CAShapeLayer with the path, colors, and line width
        circleLayer = CAShapeLayer()
        circleLayer.path = circlePath.CGPath
        circleLayer.fillColor = UIColor.clearColor().CGColor

        //I'm going to change this in the ViewController that uses this. Not the best way, I know but alas.
        circleLayer.strokeColor = UIColor.redColor().CGColor

        //You probably want to change this width
        circleLayer.lineWidth = 3.0;

        // Don't draw the circle initially
        circleLayer.strokeEnd = 0.0

        // Add the circleLayer to the view's layer's sublayers
        layer.addSublayer(circleLayer)

    }

    func setStrokeColor(color : CGColorRef) {
        circleLayer.strokeColor = color
    }


    // This is what you call if you want to draw a full circle.
    func animateCircle(duration: NSTimeInterval) {
        animateCircleTo(duration, fromValue: 0.0, toValue: 1.0)
    }

    // This is what you call to draw a partial circle.
    func animateCircleTo(duration: NSTimeInterval, fromValue: CGFloat, toValue: CGFloat){
        // We want to animate the strokeEnd property of the circleLayer
        let animation = CABasicAnimation(keyPath: "strokeEnd")

        // Set the animation duration appropriately
        animation.duration = duration

        // Animate from 0 (no circle) to 1 (full circle)
        animation.fromValue = 0
        animation.toValue = toValue

        // Do an easeout. Don't know how to do a spring instead
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)

        // Set the circleLayer's strokeEnd property to 1.0 now so that it's the
        // right value when the animation ends.
        circleLayer.strokeEnd = toValue

        // Do the actual animation
        circleLayer.addAnimation(animation, forKey: "animateCircle")
    }


    // required function
    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

Answer 1

你需要设置:

circleLayer.strokeStart = fromValue

在 animateCircleTo(duration...) 函数中。

您设置了笔画的结尾，而不是开头。因此，所有圆形动画都从 0.0 开始，即使您希望它们在笔划的后面部分开始。

像这样:

// This is what you call to draw a partial circle.
func animateCircleTo(duration: NSTimeInterval, fromValue: CGFloat, toValue: CGFloat){
    // We want to animate the strokeEnd property of the circleLayer
    let animation = CABasicAnimation(keyPath: "strokeEnd")

    // Set the animation duration appropriately
    animation.duration = duration

    // Animate from 0 (no circle) to 1 (full circle)
    animation.fromValue = 0
    animation.toValue = toValue

    // Do an easeout. Don't know how to do a spring instead
    animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)

    // Set the circleLayer's strokeEnd property to 1.0 now so that it's the
    // right value when the animation ends.
    circleLayer.strokeStart = fromValue
    circleLayer.strokeEnd = toValue

    // Do the actual animation
    circleLayer.addAnimation(animation, forKey: "animateCircle")
}