對於Uiimageview，如何在iOS swift4中將CGgradient背景顏色設置為背景顏色？

Question

var navigationImageView:UIImageView! = UIImageView()
navigationImageView.frame = (0,0,320,64)

var gradient = CAGradientLayer()
let gradientDark = UIColor(red: 148/255.0, green:210/255.0, blue: 245/255.0, alpha: 1.0)
let gradientLight = UIColor(red: 222/255.0, green:247/255.0, blue: 230/255.0, alpha: 1.0)
let gradientLight1 = UIColor(red: 245/255.0, green:247/255.0, blue: 206/255.0, alpha: 1.0)
gradient.frame = navigationImageView.bounds

let color1 = gradientDark.cgColor
let color2 = gradientLight.cgColor
let color3 = gradientLight1.cgColor

gradient.colors = [color1, color2, color3]

gradient.colors = [gradientDark.cgColor,gradientLight.cgColor,gradientLight1.cgColor];

navigationImageView.layer.insertSublayer(gradient, at: 0)

它不起作用...如何確定漸變圖像的backgorund顏色？

Answer 1

您可以從漸變制作圖像並在imageView設置

let gradient = CAGradientLayer()
let screenWidth = UIScreen.main.bounds.size.width
let defaultNavigationBarFrame = CGRect(x: 0, y: 0, width: screenWidth, height: 64)
gradient.frame = defaultNavigationBarFrame

//colors
let gradientDark = UIColor(red: 148/255.0, green:210/255.0, blue: 245/255.0, alpha: 1.0)
let gradientLight = UIColor(red: 222/255.0, green:247/255.0, blue: 230/255.0, alpha: 1.0)
let gradientLight1 = UIColor(red: 245/255.0, green:247/255.0, blue: 206/255.0, alpha: 1.0)

gradient.colors = [gradientDark.cgColor,gradientLight.cgColor,gradientLight1.cgColor]
// Create image.
let imageBG: UIImage = self.gradientImage(fromLayer: gradient)

如果要在導航欄中進行設置。

self.navigationController?.navigationBar.setBackgroundImage(imageBG,
                                                                for: .default)

從漸變創建圖像。

func gradientImage(fromLayer layer: CALayer) -> UIImage {
    UIGraphicsBeginImageContext(layer.frame.size)

    layer.render(in: UIGraphicsGetCurrentContext()!)

    let outputImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return outputImage!
}