我想创建一个树叶飘落的动画这是我的代码:privatefuncsetupEmitter(){letsize=self.bounds.sizeletemitter=CAEmitterLayer()emitter.emitterSize=CGSize(width:size.width,height:1)emitter.emitterPosition=CGPoint(x:size.width/2,y:-100)emitter.emitterShape=kCAEmitterLayerLineself.layer.addSublayer(emitter)//SHAPE1letshape1=CAE