在UIView上应用渐变不起作用 [英] Apply gradient on a UIView not working

问题描述

我正在尝试以编程方式将渐变添加到UIView，但是它不起作用.它似乎根本没有颜色.我已经附上了相关代码以及屏幕截图.请注意我正在应用渐变的底部正方形.有人可以帮我弄清楚我在做什么错吗?

I am trying to add gradient to a UIView programmatically but it is not working. It just appears to have no color at all. I have attached the relevant code as well as a screenshot. Notice the bottom square over which i am applying the gradient. Can someone help me figure out what I'm doing wrong here?

let sundayView = UIView()

override func viewDidLoad() {
    super.viewDidLoad()
    setupViews()
    setupSundayView()
}

func setupViews() {
    sundayView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(sundayView)
}

func setupSundayView() {
    sundayView.translatesAutoresizingMaskIntoConstraints = false

    NSLayoutConstraint.activateConstraints([
        sundayView.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor),
        sundayView.topAnchor.constraintEqualToAnchor(fridayView.bottomAnchor, constant: 16.0),
        sundayView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor, constant: -8.0),            
        sundayView.heightAnchor.constraintEqualToAnchor(mondayView.heightAnchor),
        sundayView.widthAnchor.constraintEqualToAnchor(mondayView.widthAnchor)
        ])

    let gradient = CAGradientLayer()
    gradient.frame = sundayView.bounds
    gradient.colors = [
        UIColor(red:1.00, green:0.37, blue:0.23, alpha:1.0).CGColor,
        UIColor(red:1.00, green:0.16, blue:0.41, alpha:1.0).CGColor
    ]
    sundayView.layer.insertSublayer(gradient, atIndex: 0)
}

推荐答案

您的渐变未显示，因为 sundayView 的 bounds 直到自动版式开始运行.覆盖 viewDidLayoutSubviews 并在那里设置渐变框架.

Your gradient isn't showing because the bounds for sundayView will not be set until Auto Layout runs. Override viewDidLayoutSubviews and set the gradient frame there.

将此属性添加到您的viewController中:

Add this property to your viewController:

var sundayGradient: CAGradientLayer?

在 setupSundayView 中，将 gradient 保存到属性:

let gradient = CAGradientLayer()
sundayGradient = gradient

然后在 viewDidLayoutSubviews 中设置框架:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    sundayGradient?.frame = sundayView.bounds
}

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