我只想运行 CAEmitterLayer 一次，我想停止birthRate 但我做不到。我想要的是它在点击屏幕时只运行一次。我一直在与代表一起尝试，但我无法让它发挥作用。你能告诉我我的代码是否有效吗？
import UIKit
import PlaygroundSupport
class Emitter {
static func get(with image: UIImage) -> CAEmitterLayer {
let emitter = CAEmitterLayer()
emitter.emitterShape = kCAEmitterLayerLine
emitter.emitterCells = generateEmitterCells(image: image)
print("emit")
emitter.setValue(0.0, forKey: "em")
return emitter
}
static func generateEmitterCells(image: UIImage) -> [CAEmitterCell] {
var cells = [CAEmitterCell]()
let cell = CAEmitterCell()
cell.contents = image.cgImage
cell.birthRate = 0.1
cell.lifetime = 20
cell.velocity = 250
cell.emissionRange = (10 * (.pi/180))
cell.scale = 0.9
cell.scaleRange = 0.3
cell.velocityRange = 100
cells.append(cell)
print("cells")
return cells
}
}
class ViewController : UIViewController{
override func viewDidLoad() {
super.viewDidLoad()
view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(handleTap)))
let view2 = UIView(frame: self.view.frame)
self.view.frame = CGRect(x: 0, y: 0, width: 320, height: 580)
super.view.backgroundColor = UIColor.white
self.view.addSubview(view2)
}
@objc func handleTap() {
rain()
}
func rain() {
let emitter = Emitter.get(with: UIImage(named: "Group 1493")!)
emitter.emitterPosition = CGPoint(x: view.frame.width / 2, y: view.frame.height + 25)
emitter.emitterSize = CGSize(width: view.frame.width, height: 2)
self.view.layer.addSublayer(emitter)
}
}
let controller = ViewController()
PlaygroundPage.current.liveView = controller.view