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)
}
}
}
使用以下代码:
extension UIView {
func applyGradient(colours: [UIColor]) -> Void {
let gradient: CAGradientLayer = CAGradientLayer()
gradient.frame = self.bounds
gradient.colors = colours.map { $0.cgColor }
gradient.startPoint = CGPoint(x : 0.0, y : 0.5)
gradient.endPoint = CGPoint(x :1.0, y: 0.5)
self.layer.insertSublayer(gradient, at: 0)
}
}
像这样调用这个函数:
self.mainView.applyGradient(colours: [.green, .blue])
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)
}
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)