ios - 雪碧包 : how to make newly spawned enemy ships shoot bullets at player?

Question

我需要帮助想出一些方法来让新生成的敌方舰艇都发射子弹。问题是我实际上不知道该怎么做。我尝试使用可变计时器，但是它只能射出一条直线，而且我无法真正控制它产生的位置。

Game Picture: There are more enemies spawning 我尝试过的:

var EnemyTimer = Foundation.Timer.scheduledTimer(timeInterval:0.3，目标:self，选择器:#selector(GameScene.spawnBullet3)，userInfo:nil，重复:true)

还尝试过:

 }
func spawnBullet3(){
    let Bullet = SKSpriteNode(imageNamed: "eBullet.png")
    Bullet.setScale(1)
    Bullet.zPosition = -1

    Bullet.position = CGPoint(x: enemy.position.x, y: enemy.position.y)

    let action = SKAction.moveTo(y: self.size.height + 100, duration: 0.5)
    let actionDone = SKAction.removeFromParent()
    Bullet.run(SKAction.sequence([action, actionDone]))

    Bullet.physicsBody = SKPhysicsBody(rectangleOf: Bullet.size)
    Bullet.physicsBody?.categoryBitMask = PhysicsCategories.Bullet
    Bullet.physicsBody!.collisionBitMask = PhysicsCategories.None
    Bullet.physicsBody?.contactTestBitMask = PhysicsCategories.Enemy
    Bullet.physicsBody?.affectedByGravity = true
    Bullet.physicsBody?.isDynamic = false
    self.addChild(Bullet)

}

Answer 1

好吧，对于初学者来说，(正如 LearnCocos2D 精彩地解释的 here ) 从不使用 Timer、performSelector:afterDelay: ，或 Grand Central Dispatch(GCD，即任何 dispatch_... 方法。

在进行任何操作之前，您必须设置几件事:

首先，将参数添加到您的spawnBullet3函数中(如果您使用自定义类，请将enemy:SKSpriteNode替换为enemy:yourCustomClass) .

func spawnBullet3(enemy:SKSpriteNode){
   let Bullet = SKSpriteNode(imageNamed: "eBullet.png")
   Bullet.setScale(1)
   Bullet.zPosition = -1

   Bullet.position = CGPoint(x: enemy.position.x, y: enemy.position.y)

   let action = SKAction.moveTo(y: self.size.height + 100, duration: 0.5)
   let actionDone = SKAction.removeFromParent()
   Bullet.run(SKAction.sequence([action, actionDone]))

   Bullet.physicsBody = SKPhysicsBody(rectangleOf: Bullet.size)
   Bullet.physicsBody?.categoryBitMask = PhysicsCategories.Bullet
   Bullet.physicsBody!.collisionBitMask = PhysicsCategories.None
   Bullet.physicsBody?.contactTestBitMask = PhysicsCategories.Enemy
   Bullet.physicsBody?.affectedByGravity = true
   Bullet.physicsBody?.isDynamic = false
   self.addChild(Bullet)
}

其次，创建一个公共(public)敌人数组(同样，如果您使用自定义类，请将 SKSpriteNode 替换为您的自定义类名称)。

var enemies:[SKSpriteNode] = []

接下来，每次创建新敌人时，将敌人追加到数组中

enemies.append(newEnemy)

现在您有两个选择:

选项 1:使用 SKAction

使用 SKAction 计时器自动每隔几秒射击一次敌人(将 SKAction.waitForDuration(2.5) 替换为 SKAction.waitForDuration(yourAmountOfSeconds)).

for e in enemies
{
   var wait = SKAction.waitForDuration(2.5)
   var run = SKAction.runBlock {
      spawnBullet3(e)
   }

   e.runAction(SKAction.repeatActionForever(SKAction.sequence([wait, run])))
}

选项 2:使用更新功能

使用update函数中的currentTime(将currentTime.truncatingRemainder(dividingBy: 3)替换为currentTime.truncatingRemainder(dividingBy: yourAmountOfSeconds)).

override func update(_ currentTime: TimeInterval) {
   [...]

   if currentTime.truncatingRemainder(dividingBy: 3) == 0
   {
      for e in enemies
      {
         spawnBullet3(e)
      }
   }
}