如何在使用NSViewRepresentable的SwiftUI应用程序中，在macOS上使用CAEmitterLayer？

Question

如何在使用NSViewRepresentable的SwiftUI应用程序中，在macOS上使用CAEmitterLayer？

swiftswiftuicaemitterlayercaemittercellnsviewrepresentable

3

我希望在基于SwiftUI的macOS应用程序中使用CAEmitterLayer。问题是：该层本身完全可见，但不会发射任何粒子。 → 这是我在GitHub上的演示项目

我基本上为一个自定义类EmitterNSView: NSView构建了一个NSViewRepresentable，它处理粒子发射器层本身。

final class EmitterNSView: NSView {

    private let emitterLayer: CAEmitterLayer = {
        let layer = CAEmitterLayer()
        layer.backgroundColor = NSColor.green.withAlphaComponent(0.33).cgColor
        return layer
    }()

    private let emitterCells: [CAEmitterCell] = {
        // https://developer.apple.com/documentation/quartzcore/caemitterlayer
        let cell = CAEmitterCell()
        cell.name = "someParticle"
        cell.birthRate = 10
        cell.lifetime = 5.0
        cell.velocity = 100
        cell.velocityRange = 50
        cell.emissionLongitude = 0.0
        cell.emissionRange = CGFloat.pi * 2.0
        cell.spinRange = 5
        cell.scale = 1.0
        cell.scaleRange = 0.25
        cell.alphaSpeed = 0.25
        cell.contents = NSImage(named: "whiteParticle.png")!.cgImage
        cell.color = NSColor.systemPink.cgColor
        cell.xAcceleration = 4
        cell.yAcceleration = 3
        cell.zAcceleration = 2
        return [cell]
    }()

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        self.wantsLayer = true
        self.layer = CALayer()
        self.layer?.autoresizingMask = [.layerWidthSizable, .layerHeightSizable]
        self.configureEmitterLayer()
        self.layer?.addSublayer(self.emitterLayer)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layout() {
        super.layout()
        self.configureEmitterLayer()
    }

    override func updateLayer() {
        super.updateLayer()
        self.configureEmitterLayer()
    }

    func configureEmitterLayer() {
        self.emitterLayer.frame = self.frame
        self.emitterLayer.autoresizingMask = [.layerHeightSizable, .layerWidthSizable]
        self.emitterLayer.masksToBounds = false
        self.emitterLayer.drawsAsynchronously = true
        self.emitterLayer.emitterMode = .points
        self.emitterLayer.birthRate = 2
        self.emitterLayer.emitterShape = CAEmitterLayerEmitterShape.line
        self.emitterLayer.emitterSize = CGSize(width: frame.width * 0.5, height: frame.height * 0.5)
        self.emitterLayer.emitterPosition = CGPoint.zero
        self.emitterLayer.renderMode = CAEmitterLayerRenderMode.additive
        self.emitterLayer.emitterCells = self.emitterCells
        self.emitterLayer.zPosition = 10
        self.emitterLayer.beginTime = CACurrentMediaTime()
        self.emitterLayer.speed = 1.5
        self.emitterLayer.emitterCells = self.emitterCells
    
    }

}

我能清楚地看到应用程序中图层的绿色背景，这意味着单元格出了问题？此时感到迷失。

在UIKit中非常相似的实现可以正常工作。

如何在基于SwiftUI的macOS应用程序中使用CAEmitterLayer？

- ixany

1个回答

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可以查看英文原文，
原文链接

- RTXGamer · Accepted Answer

在将NSImage转换为CGImage时，请使用cgImage(forProposedRect:context:hints:)。

cell.contents = NSImage(named:"whiteParticle.png").flatMap {
    return $0.cgImage(forProposedRect: nil, context: nil, hints: nil)
}