iOS CAEmitterLayer实现粒子发射动画效果

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)}

@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  }}

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)}

@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  }}

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)}

@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  }}

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)}

@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  }}

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)}

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