swift - 如何修复 "Optimization Opportunities"

Question

我正在使用 xcode 12。
我写了扩展 UI View 如下:

@IBInspectable
public var shadowRadius: CGFloat {
    get {
        return layer.shadowRadius
    }
    set {
        layer.shadowRadius = newValue
    }
}

@IBInspectable
public var shadowOpacity: Float {
    get {
        return layer.shadowOpacity
    }
    set {
         layer.shadowOpacity = newValue
    }
}

@IBInspectable
public var shadowOffset: CGSize {
    get {
        layer.shadowOffset
    }
    set {
         layer.shadowOffset = newValue
    }
}

@IBInspectable
public var shadowColor: UIColor {
    get {
        return UIColor(cgColor: layer.shadowColor ?? UIColor.clear.cgColor)
    }
    
    set {
        layer.shadowColor = newValue.cgColor
    }
}

一切正常，但是当我调试 View 时，我看到了一些像这样的紫色警告。

x-xcode-debug-views://7f8fd2258020?DBGViewDebuggerLaunchSessionParameter=7f8fd2258020:runtime: Optimization Opportunities: The layer is using dynamicshadows which are expensive to render. If possible try settingshadowPath, or pre-rendering the shadow into an image and putting itunder the layer.

有人可以向我解释这一点并帮助我摆脱它吗？

Answer 1

设置 shadowPath
一种解决方案是通过设置 shadowPath 来“引导”阴影渲染。明确满足您的需求，例如:

yourViewWithShadow.layer.shadowPath = UIBezierPath(rect: yourViewWithShadow.bounds).cgPath

确保您在正确的时间设置框架!
缓存光栅化
另一种解决方案是缓存光栅化:

yourViewWithShadow.layer.shouldRasterize = true
yourViewWithShadow.layer.rasterizationScale = UIScreen.main.scale

希望这可以帮助您消除昂贵的计算。