ios - iOS(快速)在初始化后更改CAEmitterCell的属性

Question

我的目标是使用CAEmitterLayer创建射击效果，可以通过更改给定alphaSpeed的CAEmitterCells属性的值来更改其强度。较小的alphaSpeed值将导致“轰鸣”的起火，而较大的值将抑制起火。

到目前为止，我有一个名为CAEmitterLayer的FireEmitterLayer子类，其初始化程序为:

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
 }

发射器单元是针对 UIImage数组生成的，该数组表示30x30的火焰图像:

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

每个单元格都是使用以下方法创建的:

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
}

有没有一种方法可以从此子类的某个实例(例如，某些 alphaSpeed中的 fireEmitterLayer)更改这些单元格的 UIViewController值:

var fireEmitterLayer = FireEmitterLayer(view: view)

我尝试在 FireEmitterLayer类中添加此方法

private func setAlphaSpeed(_ alphaSpeed: Float) {
    guard let emitterCells = emitterCells else { return }
    for emitterCell in emitterCells {
        emitterCell.alphaSpeed = alphaSpeed
    }
}

但这不起作用...

任何帮助表示赞赏:-)

Answer 1

每当我想使用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。

我使这些变量保持不变，使我可以动态控制单元的功能;

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。此函数的一部分制作了发射器单元，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一种方法拼凑在一起，设置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，使其最适合轰鸣或压制。在很大程度上取决于您在顶层的灵活性。