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)
}
}
}
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)
}
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)
}
Xcode 11•Swift 5.1
你可以像下面这样设计你自己的渐变视图:
@IBDesignable
public class Gradient: UIView {
@IBInspectable var startColor: UIColor = .black { didSet { updateColors() }}
@IBInspectable var endColor: UIColor = .white { didSet { updateColors() }}
@IBInspectable var startLocation: Double = 0.05 { didSet { updateLocations() }}
@IBInspectable var endLocation: Double = 0.95 { didSet { updateLocations() }}
@IBInspectable var horizontalMode: Bool = false { didSet { updatePoints() }}
@IBInspectable var diagonalMode: Bool = false { didSet { updatePoints() }}
override public class var layerClass: AnyClass { CAGradientLayer.self }
var gradientLayer: CAGradientLayer { layer as! CAGradientLayer }
func updatePoints() {
if horizontalMode {
gradientLayer.startPoint = diagonalMode ? .init(x: 1, y: 0) : .init(x: 0, y: 0.5)
gradientLayer.endPoint = diagonalMode ? .init(x: 0, y: 1) : .init(x: 1, y: 0.5)
} else {
gradientLayer.startPoint = diagonalMode ? .init(x: 0, y: 0) : .init(x: 0.5, y: 0)
gradientLayer.endPoint = diagonalMode ? .init(x: 1, y: 1) : .init(x: 0.5, y: 1)
}
}
func updateLocations() {
gradientLayer.locations = [startLocation as NSNumber, endLocation as NSNumber]
}
func updateColors() {
gradientLayer.colors = [startColor.cgColor, endColor.cgColor]
}
override public func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
super.traitCollectionDidChange(previousTraitCollection)
updatePoints()
updateLocations()
updateColors()
}
}
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]
}
}
如果你需要改变渐变的方向你必须使用startPoint和endPoint。
let gradient: CAGradientLayer = CAGradientLayer()
gradient.colors = [UIColor.blue.cgColor, UIColor.red.cgColor]
gradient.locations = [0.0 , 1.0]
gradient.startPoint = CGPoint(x: 0.0, y: 1.0)
gradient.endPoint = CGPoint(x: 1.0, y: 1.0)
gradient.frame = CGRect(x: 0.0, y: 0.0, width: self.view.frame.size.width, height: self.view.frame.size.height)
self.view.layer.insertSublayer(gradient, at: 0)
如果你想使用HEX而不是RGBA，只需拖动一个新的空的.swift并添加下面提到的代码:
import UIKit
extension UIColor {
convenience init(rgba: String) {
var red: CGFloat = 0.0
var green: CGFloat = 0.0
var blue: CGFloat = 0.0
var alpha: CGFloat = 1.0
if rgba.hasPrefix("#") {
let index = advance(rgba.startIndex, 1)
let hex = rgba.substringFromIndex(index)
let scanner = NSScanner(string: hex)
var hexValue: CUnsignedLongLong = 0
if scanner.scanHexLongLong(&hexValue) {
switch (count(hex)) {
case 3:
red = CGFloat((hexValue & 0xF00) >> 8) / 15.0
green = CGFloat((hexValue & 0x0F0) >> 4) / 15.0
blue = CGFloat(hexValue & 0x00F) / 15.0
case 4:
red = CGFloat((hexValue & 0xF000) >> 12) / 15.0
green = CGFloat((hexValue & 0x0F00) >> 8) / 15.0
blue = CGFloat((hexValue & 0x00F0) >> 4) / 15.0
alpha = CGFloat(hexValue & 0x000F) / 15.0
case 6:
red = CGFloat((hexValue & 0xFF0000) >> 16) / 255.0
green = CGFloat((hexValue & 0x00FF00) >> 8) / 255.0
blue = CGFloat(hexValue & 0x0000FF) / 255.0
case 8:
red = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
blue = CGFloat((hexValue & 0x0000FF00) >> 8) / 255.0
alpha = CGFloat(hexValue & 0x000000FF) / 255.0
default:
print("Invalid RGB string, number of characters after '#' should be either 3, 4, 6 or 8")
}
} else {
println("Scan hex error")
}
} else {
print("Invalid RGB string, missing '#' as prefix")
}
self.init(red:red, green:green, blue:blue, alpha:alpha)
}
}
类似地，拖动另一个空的.swift文件并添加下面提到的代码:
class Colors {
let colorTop = UIColor(rgba: "##8968CD").CGColor
let colorBottom = UIColor(rgba: "#5D478B").CGColor
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，在类下面实例化你的Color类，像这样:
let colors = Colors()
添加一个新函数:
func refresh() {
view.backgroundColor = UIColor.clearColor()
var backgroundLayer = colors.gl
backgroundLayer.frame = view.frame
view.layer.insertSublayer(backgroundLayer, atIndex: 0)
}
在viewDidLoad中声明函数:
refresh()
你完成了:))
如果与RGBA相比，使用HEX太容易了。: D
