iOS CAEmitterLayer实现粒子发射动画效果

iOS实现粒子发射动画效果图

代码已上传 GitHub：https://github.com/Silence-GitHub/CoreAnimationDemo

动画效果用 CAEmitterLayer 实现。CAEmitterLayer 显示粒子发射动画，具体的粒子由 CAEmitterCell 封装。代码示例是展示 CAEmitterLayer 如何使用。为了方便，直接在控制器(UIViewController)中设置 CAEmitterLayer。如果在项目中使用，有时在自定义视图(UIView)中加入 CAEmitterLayer 比较合理，例如自定义点赞按钮，可以精简控制器的代码。

下雨动画效果

这里的雨匀速下落，雨的密度逐渐变化。

给控制器添加类型为 CAEmitterLayer 的属性 rainLayer，在 viewDidLoad 方法中对此属性进行初始化

private var rainLayer: CAEmitterLayer!

private func setupRainLayer() {
  // 粒子发射图层
  rainLayer = CAEmitterLayer()
  // 发射器形状为线形，默认发射方向向上
  rainLayer.emitterShape = kCAEmitterLayerLine
  // 从发射器的轮廓发射粒子
  rainLayer.emitterMode = kCAEmitterLayerOutline
  // 优先渲染旧的粒子
  rainLayer.renderMode = kCAEmitterLayerOldestFirst
  // 发射位置
  // 对于线形发射器，线的两端点分别为
  // (emitterPosition.x - emitterSize.width/2, emitterPosition.y, emitterZPosition)和
  // (emitterPosition.x + emitterSize.width/2, emitterPosition.y, emitterZPosition)
  rainLayer.emitterPosition = CGPoint(x: view.bounds.midX, y: 0)
  // 发射器大小
  rainLayer.emitterSize = CGSize(width: view.bounds.width, height: 0)
  // 粒子生成速率的倍数，一开始不发射，设置为零
  rainLayer.birthRate = 0
  
  // 发射的粒子
  let cell = CAEmitterCell()
  // 粒子显示的内容，设置CGImage，显示图片
  cell.contents = #imageLiteral(resourceName: "Heart_red").cgImage
  // 粒子缩放倍数
  cell.scale = 0.1
  // 粒子寿命，单位是秒
  cell.lifetime = 5
  // 粒子生成速率，单位是个/秒，实际显示效果要乘以CAEmitterLayer的birthRate
  cell.birthRate = 1000
  // 粒子速度
  cell.velocity = 500
  // 粒子发射角度，正值表示顺时针方向
  cell.emissionLongitude = CGFloat.pi
  
  // 图层要发射1种粒子
  rainLayer.emitterCells = [cell]
  // 添加粒子发射图层
  view.layer.addSublayer(rainLayer)
}

点击按钮开始或停止动画。用 CABasicAnimation 使粒子生成速率的倍数渐变，达到雨逐渐变大或变小的效果

@IBAction func rainButtonClicked(_ sender: UIButton) {
  // 连续调用此方法会影响雨变大或变小的连贯性，所以禁止连续点击按钮
  sender.isUserInteractionEnabled = false
  // 粒子生成速率渐变动画
  let birthRateAnimation = CABasicAnimation(keyPath: "birthRate")
  birthRateAnimation.duration = 3
  if rainLayer.birthRate == 0 {
    // 雨变大
    birthRateAnimation.fromValue = 0
    birthRateAnimation.toValue = 1
    rainLayer.birthRate = 1
  } else {
    // 雨变小
    birthRateAnimation.fromValue = 1
    birthRateAnimation.toValue = 0
    rainLayer.birthRate = 0
  }
  // 加入动画
  rainLayer.add(birthRateAnimation, forKey: "birthRate")
  // 动画时长过后恢复按钮可点击状态
  DispatchQueue.main.asyncAfter(deadline: .now() + birthRateAnimation.duration) { [weak self] in
    guard self != nil else { return }
    sender.isUserInteractionEnabled = true
  }
}

发射一圈粒子动画效果

给控制器添加类型为 CAEmitterLayer 的属性 centerHeartLayer，在 viewDidLoad 方法中对此属性进行初始化

private var centerHeartLayer: CAEmitterLayer!

private func setupCenterHeartLayer() {
  centerHeartLayer = CAEmitterLayer()
  // 发射器形状为圆形，默认向四周发射粒子
  centerHeartLayer.emitterShape = kCAEmitterLayerCircle
  centerHeartLayer.emitterMode = kCAEmitterLayerOutline
  centerHeartLayer.renderMode = kCAEmitterLayerOldestFirst
  // 发射器位置
  // 对于圆形发射器
  // 圆心位于(emitterPosition.x, emitterPosition.y, emitterZPosition)
  // 半径为emitterSize.width
  centerHeartLayer.emitterPosition = CGPoint(x: view.bounds.midX, y: view.bounds.midY)
  centerHeartLayer.emitterSize = centerHeartButton.frame.size
  centerHeartLayer.birthRate = 0
  
  let cell = CAEmitterCell()
  cell.contents = #imageLiteral(resourceName: "Heart_red").cgImage
  cell.lifetime = 1
  cell.birthRate = 2000
  cell.scale = 0.05
  // 粒子缩放倍数每秒减小0.02，粒子逐渐缩小
  cell.scaleSpeed = -0.02
  // 粒子透明度每秒减小1，粒子逐渐变透明
  cell.alphaSpeed = -1
  cell.velocity = 30
  
  centerHeartLayer.emitterCells = [cell]
  view.layer.addSublayer(centerHeartLayer)
}

点击按钮开始动画

@IBAction func centerHeartButtonClicked(_ sender: UIButton) {
  sender.isUserInteractionEnabled = false
  // 设置动画开始时间，否则会有太多粒子
  centerHeartLayer.beginTime = CACurrentMediaTime()
  // 开始生成粒子
  centerHeartLayer.birthRate = 1
  // 一段时间后停止生成粒子
  DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) { [weak self] in
    guard let strongSelf = self else { return }
    strongSelf.centerHeartLayer.birthRate = 0
  }
  DispatchQueue.main.asyncAfter(deadline: .now() + 1) { [weak self] in
    guard self != nil else { return }
    sender.isUserInteractionEnabled = true
  }
}

向上发射一个粒子动画效果

给控制器添加类型为 CAEmitterLayer 的属性 leftHeartLayer，在 viewDidLoad 方法中对此属性进行初始化

private var leftHeartLayer: CAEmitterLayer!

private func setupLeftHeartLayer() {
  leftHeartLayer = CAEmitterLayer()
  // 点状发射器，默认发射方向向右
  // 这句可以省略，点状是默认值
  leftHeartLayer.emitterShape = kCAEmitterLayerPoint
  // 从发射器中的一点发射粒子
  // 这句可以省略，是默认值
  leftHeartLayer.emitterMode = kCAEmitterLayerVolume
  leftHeartLayer.renderMode = kCAEmitterLayerOldestFirst
  // 发射器位置
  // 对于点状发射器，发射点在(emitterPosition.x, emitterPosition.y, emitterZPosition)
  leftHeartLayer.emitterPosition = CGPoint(x: view.bounds.midX * 0.5, y: view.bounds.midY)
  leftHeartLayer.birthRate = 0
  
  let cell = CAEmitterCell()
  cell.contents = #imageLiteral(resourceName: "Heart_red").cgImage
  cell.scale = 0.5
  cell.lifetime = 1
  // 1秒发射1个粒子
  cell.birthRate = 1
  cell.alphaSpeed = -1
  cell.velocity = 50
  cell.emissionLongitude = -CGFloat.pi / 2
  
  leftHeartLayer.emitterCells = [cell]
  view.layer.addSublayer(leftHeartLayer)
}

点击按钮开始动画

@IBAction func leftHeartButtonClicked(_ sender: UIButton) {
  sender.isUserInteractionEnabled = false
  // 从上1秒开始动画，使按钮点击后立即发射粒子
  leftHeartLayer.beginTime = CACurrentMediaTime() - 1
  leftHeartLayer.birthRate = 1
  DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) { [weak self] in
    guard let strongSelf = self else { return }
    strongSelf.leftHeartLayer.birthRate = 0
  }
  DispatchQueue.main.asyncAfter(deadline: .now() + 1) { [weak self] in
    guard self != nil else { return }
    sender.isUserInteractionEnabled = true
  }
}

向上发射几个粒子动画效果

给控制器添加类型为 CAEmitterLayer 的属性 rightHeartLayer，在 viewDidLoad 方法中对此属性进行初始化

private var rightHeartLayer: CAEmitterLayer!

private func setupRightHeartLayer() {
  rightHeartLayer = CAEmitterLayer()
  rightHeartLayer.renderMode = kCAEmitterLayerOldestFirst
  rightHeartLayer.emitterPosition = CGPoint(x: view.bounds.midX * 1.5, y: view.bounds.midY)
  rightHeartLayer.birthRate = 0
  
  let cell = CAEmitterCell()
  cell.contents = #imageLiteral(resourceName: "Heart_red").cgImage
  cell.scale = 0.5
  cell.lifetime = 1
  cell.birthRate = 5
  cell.alphaSpeed = -1
  cell.velocity = 50
  cell.emissionLongitude = -CGFloat.pi / 2
  // 粒子发射角度的变化范围
  cell.emissionRange = CGFloat.pi / 4
  
  rightHeartLayer.emitterCells = [cell]
  view.layer.addSublayer(rightHeartLayer)
}

点击按钮开始动画

@IBAction func rightHeartButtonClicked(_ sender: UIButton) {
  sender.isUserInteractionEnabled = false
  // 1秒发射5个粒子，0.2秒发射1个粒子，从上0.2秒开始动画，使按钮点击后立即发射粒子
  rightHeartLayer.beginTime = CACurrentMediaTime() - 0.2
  rightHeartLayer.birthRate = 1
  DispatchQueue.main.asyncAfter(deadline: .now() + 0.8) { [weak self] in
    guard let strongSelf = self else { return }
    strongSelf.rightHeartLayer.birthRate = 0
  }
  DispatchQueue.main.asyncAfter(deadline: .now() + 1.6) { [weak self] in
    guard self != nil else { return }
    sender.isUserInteractionEnabled = true
  }
}

抛物线粒子动画效果

实现抛物线动画需要给粒子加上重力加速度。此外，这里还加入粒子旋转效果，同时发射两种粒子。

给控制器添加类型为 CAEmitterLayer 的属性 gravityLayer，在 viewDidLoad 方法中对此属性进行初始化

private var gravityLayer: CAEmitterLayer!

private func setupGravityLayer() {
  gravityLayer = CAEmitterLayer()
  gravityLayer.renderMode = kCAEmitterLayerOldestFirst
  gravityLayer.emitterPosition = CGPoint(x: 0, y: view.bounds.maxY)
  gravityLayer.birthRate = 0
  
  let cell = CAEmitterCell()
  cell.contents = #imageLiteral(resourceName: "Heart_red").cgImage
  cell.scale = 0.5
  cell.lifetime = 10
  cell.alphaSpeed = -0.1
  cell.birthRate = 10
  cell.velocity = 100
  // y轴方法的加速度，模拟重力加速度
  cell.yAcceleration = 20
  cell.emissionLongitude = -CGFloat.pi / 4
  cell.emissionRange = CGFloat.pi / 4
  // 粒子旋转角速度，单位是弧度/秒，正值表示顺时针旋转
  // 这句可以省略，默认值是零
  cell.spin = 0
  // 粒子旋转角速度变化范围
  cell.spinRange = CGFloat.pi * 2
  
  let cell2 = CAEmitterCell()
  cell2.contents = #imageLiteral(resourceName: "Heart_blue").cgImage
  cell2.scale = 0.3
  cell2.lifetime = 20
  cell2.alphaSpeed = -0.05
  cell2.birthRate = 5
  cell2.velocity = 135
  cell2.yAcceleration = 20
  cell2.emissionLongitude = -CGFloat.pi / 4
  cell2.emissionRange = CGFloat.pi / 4
  cell2.spin = 0
  cell2.spinRange = CGFloat.pi * 2
  
  // 图层要发射2种粒子
  gravityLayer.emitterCells = [cell, cell2]
  view.layer.addSublayer(gravityLayer)
}

点击开始或停止动画

@IBAction func gravityButtonClicked(_ sender: UIButton) {
  if gravityLayer.birthRate == 0 {
    gravityLayer.beginTime = CACurrentMediaTime()
    gravityLayer.birthRate = 1
  } else {
    gravityLayer.birthRate = 0
  }
}

以上是动画的实现方法，代码已上传 GitHub：https://github.com/Silence-GitHub/CoreAnimationDemo

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