swift - 如何让生成的敌舰每 x 秒发射一次子弹？

Question

我正在制作一款 spaceship 游戏，其中敌方飞船会生成并向玩家移动。

我希望敌方 spaceship 每 x 秒发射一次子弹。我尝试使用在 villain 方法内部实现的 SKAction，但它不起作用。

我想如果我能得到敌舰节点的位置我就能做到，但我做不到，因为敌舰节点在一个函数中，我无法在函数之外得到它的位置。

这是子弹方法:

func Laser(){

    let LaserBullet = SKSpriteNode(imageNamed: "Laser")

    //Physics World
    LaserBullet.physicsBody = SKPhysicsBody(rectangleOf: LaserBullet.size)
    LaserBullet.physicsBody?.categoryBitMask = NumberingPhysics.Laser
    LaserBullet.physicsBody?.contactTestBitMask = NumberingPhysics.UpperV | NumberingPhysics.YellowUpper | NumberingPhysics.UpperBlue
    LaserBullet.physicsBody?.affectedByGravity = false
    LaserBullet.physicsBody?.isDynamic = true
    LaserBullet.zPosition = 1
    LaserBullet.position = CGPoint(x: SpaceShip.position.x, y: SpaceShip.position.y). // I can put the villains location here if I can get it but I don't know how  

    let LaserThrown = SKAction.moveTo(y: frame.maxY + SpaceShip.size.height, duration: 1)

    let LaserEnded = SKAction.removeFromParent()

    run(LaserSound)
    addChild(LaserBullet)
    LaserBullet.run(SKAction.sequence([LaserThrown,LaserEnded]))
}

这是 Enemy 方法:

func RedSpawn(){
    let VillainR = Villain()

    VillainR.zPosition = 2

    VillainR.zRotation = CGFloat(Double.pi)

    let min = 0 + VillainR.size.width
    let max = self.frame.width - VillainR.size.width

    let spawn = UInt32(max-min)

    VillainR.position = CGPoint(x: CGFloat(arc4random_uniform(spawn)),y: self.size.height)

    let movement = SKAction.moveTo(y: self.frame.minY + 20, duration: 6.5)
    let remove = SKAction.removeFromParent()

    VillainR.run(SKAction.sequence([movement,remove]))

    //Physics World
    VillainR.physicsBody = SKPhysicsBody(rectangleOf: VillainR.size)
    VillainR.physicsBody?.categoryBitMask = NumberingPhysics.UpperV
    VillainR.physicsBody?.contactTestBitMask = NumberingPhysics.Laser | NumberingPhysics.SpaceShip
    VillainR.physicsBody?.affectedByGravity = false
    VillainR.physicsBody?.isDynamic = true
    VillainR.physicsBody?.collisionBitMask = 0

    addChild(VillainR)
}

这是敌人类(我认为你们不需要这个):

public class Villain: SKSpriteNode {  
    var life = 1   //Number of lives for the red villain
    var hitThisFrame = false    //Not used

   init(){
     let texture = SKTexture(imageNamed: "Villain")
     // print("number of lives: ", life)
     super.init(texture: texture, color: SKColor.clear, size: texture.size())
   }

   required public init?(coder aDecoder: NSCoder) {
      fatalError("init(coder:) has not been implemented")
   }
}

我到处搜索，但找不到答案。

提前致谢!!

Answer 1

如果我明白了，您希望每 X 秒执行一个随机的 spawnRed。正如我在您的代码中看到的，您的 spawnRed 位置是一个随机值(至少是 x 位置值)。我建议你使用 SKAction，这是我的想法。

你的 villains 函数应该是这样的(设置和创建 villains 是单独的函数):

func villains(){
let VillainR = Villain()

VillainR.zPosition = 2

VillainR.zRotation = CGFloat(Double.pi)

let min = 0 + VillainR.size.width
let max = self.frame.width - VillainR.size.width

let spawn = UInt32(max-min)

VillainR.position = CGPoint(x: CGFloat(arc4random_uniform(spawn)),y: self.size.height)

//Physics World
VillainR.physicsBody = SKPhysicsBody(rectangleOf: VillainR.size)
VillainR.physicsBody?.categoryBitMask = NumberingPhysics.UpperV
VillainR.physicsBody?.contactTestBitMask = NumberingPhysics.Laser | NumberingPhysics.SpaceShip
VillainR.physicsBody?.affectedByGravity = false
VillainR.physicsBody?.isDynamic = true
VillainR.physicsBody?.collisionBitMask = 0

let m = SKAction.moveTo(y: self.frame.minY + 20, duration: 6.5)
let remove = SKAction.removeFromParent()
VillainR.run(SKAction.sequence([movement,remove]))

addChild(VillainR)
}

对于重复的 SKAction，我认为你应该将它设置在你的 didMove() 函数中，或者作为将在 didMove() 函数中执行的另一个函数，我由于舒适和美观，更喜欢将其设置为不同的功能:

    func spawnReds() {
    let wait = SKAction.wait(forDuration: 3) //the time in seconds between each action
    let action = SKAction.run {
    self.villains() //create a villain
    }
    run(SKAction.repeatForever((SKAction.sequence([wait, action])))) // repeat this action forever = the villains function will executed every 3 seconds, which means that every 3 seconds a new villains will shout.

}

如果您在单独的函数中执行此操作，您应该在 didMove 中调用该函数，如下所示:

override func didMove(to view: SKView) {
spawnReds()
}

可以看看apple doc了解更多信息。