Question

我的目标是使用一个CAEmitterLayer来创建一个射击效果，可以通过更改给定alphaSpeed的{{1}}属性的值来更改其强度。较小的CAEmitterCells会导致“熊熊”大火，而较大的值会抑制大火。

到目前为止，我有一个alphaSpeed的子类，名为CAEmitterLayer，其初始化器由以下项给出：

FireEmitterLayer

为convenience init(view: UIView) { self.init() emitterPosition = CGPoint(x: 0.5 * view.bounds.width, y: view.bounds.height) emitterSize = CGSize(width: view.bounds.width, height: 0.05 * view.bounds.height) renderMode = .additive emitterShape = .line emitterCells = fireEmitterCells }阵列生成的发射器单元代表了30x30的火焰图像：

UIImage

每个单元格都是使用这种方法创建的：

private var fireEmitterCells: FireEmitterCells {
    var emitterCells = FireEmitterCells()
    for assetIdentifier in assetIdentifiers {
        let emitterCell = fireEmitterCell(for: assetIdentifier)
        emitterCells.append(emitterCell)
    }
    return emitterCells
}

是否有一种方法可以从此子类的某个实例（例如在某些private func fireEmitterCell(for assetIdentifier: UIImage.AssetIdentifier) -> CAEmitterCell { let fireEmitterCell = CAEmitterCell() fireEmitterCell.contents = UIImage(assetIdentifier: assetIdentifier).resized(to: CGSize(width: 20.0, height: 20.0)).cgImage fireEmitterCell.alphaSpeed = -0.3 fireEmitterCell.birthRate = fireBirthRate fireEmitterCell.lifetime = fireLifetime fireEmitterCell.lifetimeRange = 0.5 fireEmitterCell.color = UIColor.init(red: 0.8, green: 0.4, blue: 0.2, alpha: 0.6).cgColor fireEmitterCell.emissionLongitude = .pi fireEmitterCell.velocity = 80.0 fireEmitterCell.velocityRange = 5.0 fireEmitterCell.emissionRange = 0.5 fireEmitterCell.yAcceleration = -200.0 fireEmitterCell.scaleSpeed = 0.3 return fireEmitterCell }中称为alphaSpeed的实例中更改这些单元格的fireEmitterLayer值：

UIViewController

我尝试在var fireEmitterLayer = FireEmitterLayer(view: view)类中添加此方法

FireEmitterLayer

但这不起作用...

感谢您的帮助：-）

Answer 1

每当我要使用func时，我都会为发射器动态设置单元格，如下所示：

func makeEmitterCell(thisEmitter : CAEmitterLayer, newColor: UIColor, priorColor: UIColor, contentImage : UIImage) -> CAEmitterCell {

    let cell = CAEmitterCell()

    cell.birthRate = lastChosenBirthRate
    cell.lifetime = lastChosenLifetime
    cell.lifetimeRange = lastChosenLifetimeRange
    //cell.color = newColor.cgColor
    cell.emissionLongitude = lastChosenEmissionLongitude
    cell.emissionLatitude = lastChosenEmissionLatitude
    cell.emissionRange = lastChosenEmissionRange
    cell.spin = lastChosenSpin
    cell.spinRange = lastChosenSpinRange
    cell.scale = lastChosenScale
    cell.scaleRange = lastChosenScaleRange
    cell.scaleSpeed = lastChosenScaleSpeed
    cell.alphaSpeed = Float(lastChosenAlphaSpeed)
    cell.alphaRange = Float(lastChosenAlphaRange)
    cell.autoreverses = lastChosenAutoReverses
    cell.isEnabled = lastChosenIsEnabled
    cell.velocity = lastChosenVelocity
    cell.velocityRange = lastChosenVelocityRange
    cell.xAcceleration = lastChosen_X_Acceleration
    cell.yAcceleration = lastChosen_Y_Acceleration
    cell.zAcceleration = 0
    cell.contents = contentImage.cgImage

    //Access the property with this key path format: @"emitterCells.<name>.<property>"
    cell.name = "myCellName"
    let animation = CABasicAnimation(keyPath: "emitterCells.myCellName.color")
    animation.fromValue = priorColor.cgColor
    animation.toValue = newColor.cgColor
    animation.duration = CFTimeInterval(cellAnimationTimeValue)

    if thisEmitter == particleEmitter_1
    {
        particleEmitter_1.add(animation, forKey: "emitterCells.myCellName.color")
    }
    if thisEmitter == particleEmitter_2
    {
        particleEmitter_2.add(animation, forKey: "emitterCells.myCellName.color")
    }

    return cell
} // ends makeEmitterCell

在该功能的末尾，有一个我设计的彩色动画，您可以通过某种方式将其作为奖励代码获得。

我保留这些变量以使我能够随时控制细胞特征；

var lastChosenBirthRate : Float = 300
var lastChosenLifetime : Float = 3
var lastChosenLifetimeRange : Float = 0
var lastChosenEmissionLongitude : CGFloat = 2 * CGFloat.pi
var lastChosenEmissionLatitude : CGFloat = 2 * CGFloat.pi
var lastChosenEmissionRange : CGFloat = 2 * CGFloat.pi
var lastChosenSpin : CGFloat = 1
var lastChosenSpinRange : CGFloat = 0
var lastChosenScale : CGFloat = 1
var lastChosenScaleRange : CGFloat = 0
var lastChosenScaleSpeed : CGFloat = -0.3
var lastChosenAlphaSpeed : CGFloat = -0.1
var lastChosenAlphaRange : CGFloat = 0
var lastChosenAutoReverses : Bool = false
var lastChosenIsEnabled : Bool = true
var lastChosenVelocity : CGFloat = 20
var lastChosenVelocityRange : CGFloat = 0
var lastChosen_X_Acceleration : CGFloat = 0
var lastChosen_Y_Acceleration : CGFloat = 0

我在代码中的多个位置制作了发射器单元。这是一个。此函子的一部分将制作发射器单元并将其设置为所需的发射器：

func changeParticlesCellImageRightNow(thisEmitter : CAEmitterLayer, thisContentImage : UIImage, theColor : UIColor)
{
    var priorColorToPassDown = UIColor()

    if thisEmitter == particleEmitter_1
    {
        priorColorToPassDown = lastColorUsedEmitter1
    }
    if thisEmitter == particleEmitter_2
    {
        priorColorToPassDown = lastColorUsedEmitter2
    }

    let color1 = makeEmitterCell(thisEmitter: thisEmitter, newColor: theColor, priorColor: priorColorToPassDown, contentImage: thisContentImage)

    thisEmitter.emitterCells = [color1]

}  // ends changeParticlesCellImageRightNow

这里是对该函数的调用：

    // Force the change to occur right now, using the existing colors
    changeParticlesCellImageRightNow(thisEmitter : particleEmitter_1, thisContentImage : emitter_1_Image, theColor : lastColorUsedInGeneral)
    changeParticlesCellImageRightNow(thisEmitter : particleEmitter_2, thisContentImage : emitter_2_Image, theColor : lastColorUsedInGeneral)

这是发射器层对象

let particleEmitter_1 = CAEmitterLayer()
let particleEmitter_2 = CAEmitterLayer()

您可能能够以类似的方式将方法拼凑在一起，将发射器细胞的出生率，速度，速度范围，alpha速度，比例，比例范围，比例速度等设置为最适合轰鸣或压制。在很大程度上取决于您在顶层的灵活性。

iOS（快速）在初始化后更改CAEmitterCell的属性

1 个答案: