var emitter = CAEmitterLayer()
    emitter.emitterPosition = CGPoint(x: self.view.frame.size.width / 2,y: -10)
    emitter.emitterShape = kCAEmitterLayerLine
    emitter.emitterSize = CGSize(width: self.view.frame.size.width,height: 2.0)
    emitter.emitterCells = generateEmitterCells()
    self.view.layer.addSublayer(emitter)

在这里,CAEmitterLayer涵盖了我的观点…… self.view的内容不可见..

参考.代码：https://oktapodi.github.io/2017/05/08/particle-effects-in-swift-using-caemitterlayer.html

我想在我的视图上设置这个动画.