当我试图在swift中绘制渐变时出现问题

Question

当我尝试在Swift代码中绘制渐变时出现错误：

  

GradientView.swift：31：40：找不到接受提供参数的'__conversion'的重载

这是我的代码：

let context: CGContextRef = UIGraphicsGetCurrentContext()
let locations: CGFloat[] = [ 0.0, 0.25, 0.5, 0.75 ]
let colors = [UIColor.redColor().CGColor, UIColor.greenColor().CGColor,UIColor.blueColor().CGColor, UIColor.yellowColor().CGColor]
let colorspace: CGColorSpaceRef = CGColorSpaceCreateDeviceRGB()
let gradient: CGGradientRef = CGGradientCreateWithColors(colorspace, colors, locations)
//CGGradientCreateWithColors(colorspace,colors,locations)
let startPoint: CGPoint = CGPointMake(0, 0)
let endPoint: CGPoint = CGPointMake(500,500)
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);

问题是CGGradientCreateWithColors采用CFArray而不是普通的Swift数组。我不知道如何将CFArray转换为Array，并且在Apple的文档中找不到任何内容。任何的想法？感谢

Answer 1

Swift 3

let colors = [UIColor.red.cgColor, UIColor.green.cgColor,
  UIColor.blue.cgColor, UIColor.yellow.cgColor
  ] as CFArray

Swift 2

您可以使用显式类型CFArray注释常量：

let colors: CFArray = [UIColor.redColor().CGColor, ...

Answer 2

这可能会有所帮助：

import CoreGraphics

import Foundation
import UIKit

class GradientLabel : UILabel {

    let gradient:               CGGradient!
    let alignedToSuperview:     Bool!

    init(colors: [UIColor]!, locations: [CGFloat]!, alignedToSuperview: Bool = true) {
        super.init(frame: CGRect.zeroRect)

        let gradientColors = colors.map {(color: UIColor!) -> AnyObject! in return color.CGColor as AnyObject! } as NSArray
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        self.gradient = CGGradientCreateWithColors(colorSpace, gradientColors, locations)
        self.alignedToSuperview = alignedToSuperview
    }

    override func drawTextInRect(rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()

        CGContextSaveGState(context) ;
        CGContextSetTextDrawingMode(context, kCGTextFill) ;

        super.drawTextInRect(rect) ;

        let lines = CGRect (origin: CGPoint(x: 0, y:16.0), size: CGSize(width: 160.0, height: 2.0)) ;
        CGContextSetFillColorWithColor(context, UIColor.whiteColor().CGColor) ;
        CGContextFillRect(context, lines) ;

        // snapshot the context into the just created mask
        let alphaMask = CGBitmapContextCreateImage(context) ;

        CGContextClearRect(context, rect) ;

        CGContextTranslateCTM(context, 0, rect.size.height);
        CGContextScaleCTM(context, 1.0, -1.0);

        CGContextClipToMask(context, rect, alphaMask);

        let startPoint = CGPoint(x:0.0, y: 0.0)
        let endPoint = CGPoint(x:self.superview.bounds.size.width, y: 0.0)

        if self.alignedToSuperview {
            CGContextTranslateCTM(context, -1.0 * self.frame.origin.x, 0.0)
        }

//        var options: CGGradientDrawingOptions = kCGGradientDrawsBeforeStartLocation as CGGradientDrawingOptions
//            | kCGGradientDrawsAfterEndLocation GGradientDrawsBeforeStartLocation as UInt32 ;
//        CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, options) ;
        CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 3)

        CGContextRestoreGState(context)
    }
}

也分享为：https://gist.github.com/verec/238ee65968321c0e78a3，显示示例用途。

Answer 3

在我的代码中，我不得不强行打开CGColor的值：

collectionRadient.colors = [ UIColor.redColor().CGColor!,UIColor.purpleColor().CGColor!]

也许这可以帮助你;）...

Answer 4

也许这个？

colors.bridgeToObjectiveC() as CFArray