我试图应用渐变作为一个视图(故事板的主视图)的背景色。代码运行,但没有任何变化。我使用xCode Beta 2和Swift。

代码如下:

class Colors {
  let colorTop = UIColor(red: 192.0/255.0, green: 38.0/255.0, blue: 42.0/255.0, alpha: 1.0)
  let colorBottom = UIColor(red: 35.0/255.0, green: 2.0/255.0, blue: 2.0/255.0, alpha: 1.0)

  let gl: CAGradientLayer

  init() {
    gl = CAGradientLayer()
    gl.colors = [ colorTop, colorBottom]
    gl.locations = [ 0.0, 1.0]
  }
}

然后在视图控制器中:

  let colors = Colors()

  func refresh() {
        view.backgroundColor = UIColor.clearColor()
        var backgroundLayer = colors.gl
        backgroundLayer.frame = view.frame
        view.layer.insertSublayer(backgroundLayer, atIndex: 0)
      }
    }
  }

当前回答

你提供给渐变的颜色必须是CGColor类型。设置CGColor数组为gl。colors。

正确的代码是:

class Colors {
    var gl:CAGradientLayer!

    init() {
        let colorTop = UIColor(red: 192.0 / 255.0, green: 38.0 / 255.0, blue: 42.0 / 255.0, alpha: 1.0).cgColor
        let colorBottom = UIColor(red: 35.0 / 255.0, green: 2.0 / 255.0, blue: 2.0 / 255.0, alpha: 1.0).cgColor

        self.gl = CAGradientLayer()
        self.gl.colors = [colorTop, colorBottom]
        self.gl.locations = [0.0, 1.0]
    }
}

其他回答

用这个自定义类扩展UIView。


GradientView.swift

import UIKit

class GradientView: UIView {

    // Default Colors
    var colors:[UIColor] = [UIColor.redColor(), UIColor.blueColor()]

    override func drawRect(rect: CGRect) {

        // Must be set when the rect is drawn
        setGradient(colors[0], color2: colors[1])
    }

    func setGradient(color1: UIColor, color2: UIColor) {

        let context = UIGraphicsGetCurrentContext()
        let gradient = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), [color1.CGColor, color2.CGColor], [0, 1])!

        // Draw Path
        let path = UIBezierPath(rect: CGRectMake(0, 0, frame.width, frame.height))
        CGContextSaveGState(context)
        path.addClip()
        CGContextDrawLinearGradient(context, gradient, CGPointMake(frame.width / 2, 0), CGPointMake(frame.width / 2, frame.height), CGGradientDrawingOptions())
        CGContextRestoreGState(context)
    }

    override func layoutSubviews() {

        // Ensure view has a transparent background color (not required)
        backgroundColor = UIColor.clearColor()
    }

}

使用

gradientView。colors = [uiccolor . blackcolor ().colorWithAlphaComponent(0.8), uiccolor . clearcolor ()]


结果

只是修改上面提到的答案。

func setGradientBackground() {
    let colorTop =  UIColor(red: 255.0/255.0, green: 149.0/255.0, blue: 0.0/255.0, alpha: 1.0).cgColor
    let colorBottom = UIColor(red: 255.0/255.0, green: 94.0/255.0, blue: 58.0/255.0, alpha: 1.0).cgColor
                
    let gradientLayer = CAGradientLayer()
    gradientLayer.colors = [colorTop, colorBottom]
    gradientLayer.locations = [0.0, 1.0]
    gradientLayer.frame = self.view.bounds
            
    self.view.layer.insertSublayer(gradientLayer, at:0)
}

然后在viewWillAppear中调用这个方法

override func viewWillAppear(_ animated: Bool) {
    setGradientBackground()
    super.viewWillAppear(animated)
}

对于那些想要Objective C版本的答案的人。经过测试,在iOS13上运行

// Done here so that constraints have completed and the frame is correct.
- (void) viewDidLayoutSubviews { 
    [super viewDidLayoutSubviews];
    UIColor *colorTop = [UIColor colorWithRed:(CGFloat)192.0/255.0 green: 38.0/255.0 blue: 42.0/255.0 alpha:1.0];
    UIColor *colorBottom = [UIColor colorWithRed: 35.0/255.0 green: 2.0/255.0 blue: 2.0/255.0 alpha: 1.0];
    CAGradientLayer *gl = [CAGradientLayer new];
    [gl setColors:@[(id)[colorTop CGColor], (id)[colorBottom CGColor]]];
    [gl setLocations:@[@0.0f, @1.0f]];
    self.view.backgroundColor = [UIColor clearColor];
    CALayer *backgroundLayer = gl;
    backgroundLayer.frame = self.view.frame;
    [self.view.layer insertSublayer:backgroundLayer atIndex:0];
}

我把罗希特·西索迪亚和米高梅的答案混在了一起

// MARK: - Gradient

public enum CAGradientPoint {
    case topLeft
    case centerLeft
    case bottomLeft
    case topCenter
    case center
    case bottomCenter
    case topRight
    case centerRight
    case bottomRight
    var point: CGPoint {
        switch self {
        case .topLeft:
            return CGPoint(x: 0, y: 0)
        case .centerLeft:
            return CGPoint(x: 0, y: 0.5)
        case .bottomLeft:
            return CGPoint(x: 0, y: 1.0)
        case .topCenter:
            return CGPoint(x: 0.5, y: 0)
        case .center:
            return CGPoint(x: 0.5, y: 0.5)
        case .bottomCenter:
            return CGPoint(x: 0.5, y: 1.0)
        case .topRight:
            return CGPoint(x: 1.0, y: 0.0)
        case .centerRight:
            return CGPoint(x: 1.0, y: 0.5)
        case .bottomRight:
            return CGPoint(x: 1.0, y: 1.0)
        }
    }
}

extension CAGradientLayer {

    convenience init(start: CAGradientPoint, end: CAGradientPoint, colors: [CGColor], type: CAGradientLayerType) {
        self.init()
        self.frame.origin = CGPoint.zero
        self.startPoint = start.point
        self.endPoint = end.point
        self.colors = colors
        self.locations = (0..<colors.count).map(NSNumber.init)
        self.type = type
    }
}

extension UIView {

    func layerGradient(startPoint:CAGradientPoint, endPoint:CAGradientPoint ,colorArray:[CGColor], type:CAGradientLayerType ) {
        let gradient = CAGradientLayer(start: .topLeft, end: .topRight, colors: colorArray, type: type)
        gradient.frame.size = self.frame.size
        self.layer.insertSublayer(gradient, at: 0)
    }
}

To Use写:-

        btnUrdu.layer.cornerRadius = 25
        btnUrdu.layer.masksToBounds = true 
        btnUrdu.layerGradient(startPoint: .centerRight, endPoint: .centerLeft, colorArray: [UIColor.appBlue.cgColor, UIColor.appLightBlue.cgColor], type: .axial)

输出:

有一个名为Chameleon (https://github.com/viccalexander/Chameleon)的库可以用于渐变颜色。它甚至有渐变的风格来实现。这就是如何在swift 4 podfile中添加它 “变色龙框架/Swift”,:git => 'https://github.com/ViccAlexander/Chameleon.git',:branch => 'wip/swift4'

import ChameleonFramework

let colors:[UIColor] = [
  UIColor.flatPurpleColorDark(), 
  UIColor.flatWhiteColor()
]
view.backgroundColor = GradientColor(.TopToBottom, frame: view.frame, colors: colors)