[SpriteKit] 系统框架中Cocos2d-x制作小游戏ZombieConga

概述

使用SpriteKit实现一个简单的游戏, 通过一个游戏来进行SpriteKit的入门, 熟练2D游戏的API, 也可以更好的结合在iOS应用中.

详细

代码下载：http://www.demodashi.com/demo/10667.html

今天我们进入一个全新的系列，先熟悉SpriteKit，然后再看实战的游戏案例。

一、了解SpriteKit

本期的内容就是使用SpriteKit实现一个简单的游戏, 通过一个游戏来进行SpriteKit的入门, 熟练2D游戏的API, 也可以更好的结合在iOS应用中, SpriteKit和Cocos2d 一样都是一个模式, 就是场景, 精灵之类的, 也都是操作Node节点, 我们先来看下基本的API, 以便更好的理解.

SKNode

open class SKNode : UIResponder, NSCopying, NSCoding, UIFocusItem
      open var name: String?
      open var position: CGPoint
      open var zPosition: CGFloat
      open var zRotation: CGFloat
      open func addChild(_ node: SKNode)
      open func removeFromParent()
      open func enumerateChildNodes(withName name: String, using block: @escaping (SKNode, UnsafeMutablePointer<ObjCBool>) -> Swift.Void)
      open func run(_ action: SKAction, completion block: @escaping () -> Swift.Void)
      open func run(_ action: SKAction, withKey key: String)
      open func hasActions() -> Bool
      open func removeAllActions()
      open func intersects(_ node: SKNode) -> Bool

SpriteKit中所有节点的父类, 不直接操作, 类似于CAAnimation

name: 节点的名字, 对节点进行标识
position: 节点的位置, SpriteKit坐标系与UIKit不同
zPosition: Z轴上的位置, 用于显示节点的前后顺序
zRotation: 旋转的弧度
addChild: 添加子节点, 类似于addSubView
removeFromParent: 删除子节点, 类似于removeFromSuperView
enumerateChildNodes: 遍历子节点
run: 执行行动
hasActions: 是否有行动
removeAllActions: 删除所有行动
intersects: 节点之间是否有交集

SKSpriteNode

open class SKSpriteNode : SKNode, SKWarpable
    public convenience init(imageNamed name: String)

Sprite和UIkit中的ImageView非常相似, 游戏中的每一个显示出来的图像都可以使用精灵

SKTexture

open class SKTexture : NSObject, NSCopying, NSCoding

纹理, 目前可知可以实现类似imageView的动画效果, 待深究

SKShapeNode

open class SKShapeNode : SKNode
    open var path: CGPath?
    open var strokeColor: UIColor
    open var fillColor: UIColor
    open var lineWidth: CGFloat

与CAShapeLayer及Quartz2D的部分API极度相似, 和H5中的Canvas也很类似

SKLabelNode

open class SKLabelNode : SKNode 
    public convenience init(text: String?)
    public init(fontNamed fontName: String?)
    open var verticalAlignmentMode: SKLabelVerticalAlignmentMode
    open var horizontalAlignmentMode: SKLabelHorizontalAlignmentMode
    open var fontSize: CGFloat
    open var fontColor: UIColor?

类似于UILabel, 与字体颜色和对齐属性等字段, 垂直对齐包括上, 中, 基线, 下, 水平对齐包括,左, 中, 右

SKCameraNode

open class SKCameraNode : SKNode

摄像机节点, 摄像机的position永远在屏幕中

SKAction

open class SKAction : NSObject, NSCopying, NSCoding

    open class func moveBy(x deltaX: CGFloat, y deltaY: CGFloat, duration sec: TimeInterval) -> SKAction
    open class func move(to location: CGPoint, duration sec: TimeInterval) -> SKAction
    open class func rotate(byAngle radians: CGFloat, duration sec: TimeInterval) -> SKAction
    open class func rotate(toAngle radians: CGFloat, duration sec: TimeInterval) -> SKAction
    open class func scale(by scale: CGFloat, duration sec: TimeInterval) -> SKAction
    open class func scale(to scale: CGFloat, duration sec: TimeInterval) -> SKAction

    open class func sequence(_ actions: [SKAction]) -> SKAction
    open class func group(_ actions: [SKAction]) -> SKAction
    open class func `repeat`(_ action: SKAction, count: Int) -> SKAction
    open class func repeatForever(_ action: SKAction) -> SKAction
    open class func wait(forDuration sec: TimeInterval) -> SKAction
    open class func removeFromParent() -> SKAction
    open class func run(_ block: @escaping () -> Swift.Void) -> SKAction

Action和Core Animataion非常相似, 包括了移动, 旋转, 缩放的动画

sequence 行动序列, 逐个执行行动, 串行
group 组, 类似于CAAnimationGroup 将行动包装在组中同时执行, 并行
repeat(:count:) 重复次数
repeatForever: 一直重复执行
wait: 等待执行
removeFromParent: 移除行动
run: 类似于基本动画的animate闭包, 执行闭包中的动作

SKSence

open class SKScene : SKEffectNode
    public init(size: CGSize)
    open var scaleMode: SKSceneScaleMode
@available(iOS 9.0, *)
    weak open var camera: SKCameraNode?
    open var anchorPoint: CGPoint
    open func update(_ currentTime: TimeInterval)
    open func didEvaluateActions()
    open func didMove(to view: SKView)

Sence类似于ViewController, 可以进行场景的切换

size: 场景的尺寸
scaleMode: 缩放模式
camera: 摄像头
anchorPoint: 锚点, 和Layer层相同, 但坐标系不同
update: 刷帧, 每一帧都会调用的方法用于渲染
didEvaluateActions: 生命周期方法, 当行动加载完成后调用
didMove(to view: SKView): 当场景被移到View上调用,类似于viewDidLoad

SKTransition

open class SKTransition : NSObject, NSCopying

转场效果, 类似于基本动画的transition

SKView

open class SKView : UIView
    open var ignoresSiblingOrder: Bool
    open func presentScene(_ scene: SKScene, transition: SKTransition)

UIView的子类, 承载场景的View, 所有游戏的效果都在这个View中实现, 类似于导航控制器的角色

ignoresSiblingOrder: 是否忽略同级元素
presentScene: 切换场景

二、小游戏实战案例

API, 了解一些基本的就够了, 如果要深究可以打开头文件逐个尝试, 我们现在就来实现一个小游戏, 这个游戏中包含了三种角色, 僵尸, 老太和猫, 当僵尸吃到15个猫即为胜利, 僵尸被老太打到5次即为失败, 我们着手进行游戏的开发吧!

Step1 创建游戏后自动生成GameViewController, 将其加载自定义的场景

class GameViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    let scene =
      MainMenuScene(size:CGSize(width: 2048, height: 1536)) //进行主场景的设置
    let skView = self.view as! SKView
    skView.showsFPS = true //显示帧率
    skView.showsNodeCount = true //显示节点个数
    skView.ignoresSiblingOrder = true // 忽略同级元素优先级
    scene.scaleMode = .aspectFill // 缩放模式设置填充适配
    skView.presentScene(scene) //显示场景
  }
}

Step2 注意点: 由于与UIKit坐标系不同, SpriteKit的坐标系中, 由于锚点默认为(0.5, 0.5), position的位置y轴向上取大.

class MainMenuScene: SKScene {

  override func didMove(to view: SKView) { //到场景被加入时调用
    let background = SKSpriteNode(imageNamed: "MainMenu") //设置背景图片
    background.position = CGPoint(x: size.width/2, y: size.height/2) /将图片设置为居中显示
    addChild(background) //添加到场景中
  }

  func sceneTapped() { //场景点击时调用
    let myScene = GameScene(size: size) //创建游戏场景
    myScene.scaleMode = scaleMode //赋值缩放模式
    let reveal = SKTransition.doorway(withDuration: 1.5) //设置转场模式及时间
    view?.presentScene(myScene, transition: reveal) //切换场景
  }

  override func touchesBegan(_ touches: Set<UITouch>, 
                             with event: UIEvent?) {
    sceneTapped() //调用场景被点击方法
  }

}

Step3 设置游戏场景的属性, 注意点, 速度包括方向和增量

class GameScene: SKScene {

    let zombie = SKSpriteNode(imageNamed: "zombie1") //僵尸节点
    var lastUpdateTime: TimeInterval = 0 //最后更新时间
    var dt: TimeInterval = 0 //增量
    let zombieMovePointsPerSec: CGFloat = 480.0 //每秒僵尸移动距离
    var velocity = CGPoint.zero //速度
    let playableRect: CGRect //可执行区域
    var lastTouchLocation: CGPoint? //最后触摸点
    let zombieRotateRadiansPerSec:CGFloat = 4.0 * π //每秒僵尸旋转的弧度
    let zombieAnimation: SKAction //僵尸动画
    let catCollisionSound: SKAction = SKAction.playSoundFileNamed( //猫音效
        "hitCat.wav", waitForCompletion: false)
    let enemyCollisionSound: SKAction = SKAction.playSoundFileNamed( //老太音效
        "hitCatLady.wav", waitForCompletion: false)
    var invincible = false //是否无敌
    let catMovePointsPerSec:CGFloat = 480.0 //猫每秒移动的距离
    var lives = 5 //设置5条命
    var gameOver = false //是否游戏结束
    let cameraNode = SKCameraNode() //摄像机
    let cameraMovePointsPerSec: CGFloat = 200.0 //摄像机每秒移动的距离
    let livesLabel = SKLabelNode(fontNamed: "Glimstick") //生命数量标签
    let catsLabel = SKLabelNode(fontNamed: "Glimstick") //捕获猫数量的标签

    var cameraRect : CGRect { //摄像头区域计算属性
    let x = cameraNode.position.x - size.width/2
        + (size.width - playableRect.width)/2
    let y = cameraNode.position.y - size.height/2
        + (size.height - playableRect.height)/2
    return CGRect(
      x: x,
      y: y,
      width: playableRect.width, 
      height: playableRect.height)
  }
    ...
}

Step4 场景的初始化方法的设置

override init(size: CGSize) {
    let maxAspectRatio:CGFloat = 16.0/9.0 //设置屏幕比率为 16比9
    let playableHeight = size.width / maxAspectRatio
    let playableMargin = (size.height-playableHeight)/2.0
    playableRect = CGRect(x: 0, y: playableMargin, 
                          width: size.width,
                          height: playableHeight)

    // 1
    var textures:[SKTexture] = [] //纹理数组
    // 2
    for i in 1...4 {
      textures.append(SKTexture(imageNamed: "zombie\(i)")) //类似imageView动画
    }
    // 3
    textures.append(textures[2])
    textures.append(textures[1])

    // 4
    zombieAnimation = SKAction.animate(with: textures,  //僵尸动画执行纹理
      timePerFrame: 0.1)

    super.init(size: size)
  }

Step5 这个没什么好说的, 就是花一条屏幕的线, 来看碰撞检测用的

func debugDrawPlayableArea() { //测试可操作区域
    let shape = SKShapeNode() 
    let path = CGMutablePath()
    path.addRect(playableRect)
    shape.path = path
    shape.strokeColor = SKColor.red
    shape.lineWidth = 4.0
    addChild(shape)
  }

Step6 当场景被加载的时候进行一些设置和操作

override func didMove(to view: SKView) {

    playBackgroundMusic(filename: "backgroundMusic.mp3") //播放背景音乐

    for i in 0...1 { //进行场景的设置
      let background = backgroundNode() //合并成一个大场景
      background.anchorPoint = CGPoint.zero
      background.position = 
        CGPoint(x: CGFloat(i)*background.size.width, y: 0)
      background.name = "background"
      background.zPosition = -1 //设置为-1, 保持添加新节点永远在背景之上
      addChild(background)
    }

    zombie.position = CGPoint(x: 400, y: 400)  
    zombie.zPosition = 100
    addChild(zombie) //将僵尸添加入场景
    // zombie.run(SKAction.repeatForever(zombieAnimation))

    run(SKAction.repeatForever( //场景执行行动
      SKAction.sequence([SKAction.run() { [weak self] in
                      self?.spawnEnemy() //添加老太
                    },
                    SKAction.wait(forDuration: 2.0)]))) //等待2秒

    run(SKAction.repeatForever(
      SKAction.sequence([SKAction.run() { [weak self] in
                          self?.spawnCat() //添加猫
                        },
                        SKAction.wait(forDuration: 1.0)]))) //等待1秒

    // debugDrawPlayableArea()

    addChild(cameraNode) //添加摄像头节点
    camera = cameraNode
    cameraNode.position = CGPoint(x: size.width/2, y: size.height/2)

    livesLabel.text = "Lives: X" //命数显示的设置
    livesLabel.fontColor = SKColor.black
    livesLabel.fontSize = 100
    livesLabel.zPosition = 150
    livesLabel.horizontalAlignmentMode = .left //左下角
    livesLabel.verticalAlignmentMode = .bottom
    livesLabel.position = CGPoint( 
      x: -playableRect.size.width/2 + CGFloat(20),
      y: -playableRect.size.height/2 + CGFloat(20))
    cameraNode.addChild(livesLabel)

    catsLabel.text = "Cats: X" //猫数显示的设置
    catsLabel.fontColor = SKColor.black
    catsLabel.fontSize = 100
    catsLabel.zPosition = 150
    catsLabel.horizontalAlignmentMode = .right //右下角
    catsLabel.verticalAlignmentMode = .bottom
    catsLabel.position = CGPoint(x: playableRect.size.width/2 - CGFloat(20),
      y: -playableRect.size.height/2 + CGFloat(20))
    cameraNode.addChild(catsLabel)

  }

Step7 背景音乐的处理

import AVFoundation

var backgroundMusicPlayer: AVAudioPlayer!

func playBackgroundMusic(filename: String) { 
  let resourceUrl = Bundle.main.url(forResource: //从沙盒中读取音乐
    filename, withExtension: nil)
  guard let url = resourceUrl else {
    print("Could not find file: \(filename)")
    return
  }

  do { 
    try backgroundMusicPlayer = //如果路径错误或文件损坏抛出异常
      AVAudioPlayer(contentsOf: url)
    backgroundMusicPlayer.numberOfLoops = -1
    backgroundMusicPlayer.prepareToPlay()
    backgroundMusicPlayer.play()
  } catch {
    print("Could not create audio player!")
    return
  }
}

Step8 进行背景节点的拼接

func backgroundNode() -> SKSpriteNode {
    // 1
    let backgroundNode = SKSpriteNode()
    backgroundNode.anchorPoint = CGPoint.zero
    backgroundNode.name = "background"

    // 2
    let background1 = SKSpriteNode(imageNamed: "background1")
    background1.anchorPoint = CGPoint.zero
    background1.position = CGPoint(x: 0, y: 0)
    backgroundNode.addChild(background1)

    // 3
    let background2 = SKSpriteNode(imageNamed: "background2") //将第二张图拼接在第一张图的后面
    background2.anchorPoint = CGPoint.zero
    background2.position =
      CGPoint(x: background1.size.width, y: 0)
    backgroundNode.addChild(background2)

    // 4
    backgroundNode.size = CGSize(
      width: background1.size.width + background2.size.width,
      height: background1.size.height)
    return backgroundNode
  }

Step9 设置老太的显示和行动

func spawnEnemy() {
    let enemy = SKSpriteNode(imageNamed: "enemy") //添加老太节点
    enemy.position = CGPoint(
      x: cameraRect.maxX + enemy.size.width/2,
      y: CGFloat.random( //随机高度出现
        min: cameraRect.minY + enemy.size.height/2,
        max: cameraRect.maxY - enemy.size.height/2))
    enemy.zPosition = 50
    enemy.name = "enemy"
    addChild(enemy)

    let actionMove = //进行老太的行动
      SKAction.moveBy(x: -(size.width + enemy.size.width), y: 0, duration: 2.0)
    let actionRemove = SKAction.removeFromParent()
    enemy.run(SKAction.sequence([actionMove, actionRemove])) //当移动完成后删除老太节点
  }

Step10 设置猫的显示和行动

func spawnCat() {
    // 1
    let cat = SKSpriteNode(imageNamed: "cat") //添加猫节点
    cat.name = "cat"
    cat.position = CGPoint(
      x: CGFloat.random(min: cameraRect.minX, //随机位置出现
                        max: cameraRect.maxX),
      y: CGFloat.random(min: cameraRect.minY,
                        max: cameraRect.maxY))
    cat.zPosition = 50
    cat.setScale(0) //初始缩放设为0
    addChild(cat)
    // 2
    let appear = SKAction.scale(to: 1.0, duration: 0.5) //

    cat.zRotation = -π / 16.0 //设置初始旋转
    let leftWiggle = SKAction.rotate(byAngle: π/8.0, duration: 0.5) //左边转
    let rightWiggle = leftWiggle.reversed() //右边转
    let fullWiggle = SKAction.sequence([leftWiggle, rightWiggle]) //左边转后右边转

    let scaleUp = SKAction.scale(by: 1.2, duration: 0.25) //进行放大
    let scaleDown = scaleUp.reversed() //缩小
    let fullScale = SKAction.sequence( //放大后缩小
      [scaleUp, scaleDown, scaleUp, scaleDown])
    let group = SKAction.group([fullScale, fullWiggle]) //同时执行缩放和旋转
    let groupWait = SKAction.repeat(group, count: 10) //重复10次组动画

    let disappear = SKAction.scale(to: 0, duration: 0.5) //缩放消失
    let removeFromParent = SKAction.removeFromParent() //移除节点
    let actions = [appear, groupWait, disappear, removeFromParent] //执行行动
    cat.run(SKAction.sequence(actions)) //节点执行行动
  }

Step11 随机数的设置

extension CGFloat {
  static func random() -> CGFloat {
    return CGFloat(Float(arc4random()) / Float(UInt32.max))
  }

  static func random(min: CGFloat, max: CGFloat) -> CGFloat {
    assert(min < max)
    return CGFloat.random() * (max - min) + min
  }
}

Step12 进行每帧的逻辑

override func update(_ currentTime: TimeInterval) {

    if lastUpdateTime > 0 { //算出每帧的增量
      dt = currentTime - lastUpdateTime
    } else {
      dt = 0
    }
    lastUpdateTime = currentTime

    /*
    if let lastTouchLocation = lastTouchLocation {
      let diff = lastTouchLocation - zombie.position
      if diff.length() <= zombieMovePointsPerSec * CGFloat(dt) {
        zombie.position = lastTouchLocation
        velocity = CGPoint.zero
        stopZombieAnimation()
      } else {
      */
        move(sprite: zombie, velocity: velocity) //移动僵尸 基于算法
        rotate(sprite: zombie, direction: velocity,  //旋转僵尸 基于算法
          rotateRadiansPerSec: zombieRotateRadiansPerSec)
      /*}
    }*/

    boundsCheckZombie() //边界监测
    // checkCollisions()
    moveTrain() //捕获操作
    moveCamera() //移动摄像头
    livesLabel.text = "Lives: \(lives)" //更新命数

    if lives <= 0 && !gameOver { //当命用完的时候
      gameOver = true
      print("You lose!")
      backgroundMusicPlayer.stop() //停止背景音乐

      // 1
      let gameOverScene = GameOverScene(size: size, won: false)
      gameOverScene.scaleMode = scaleMode
      // 2
      let reveal = SKTransition.flipHorizontal(withDuration: 0.5)
      // 3
      view?.presentScene(gameOverScene, transition: reveal) //切换场景
    }

    // cameraNode.position = zombie.position

  }

Step13 僵尸移动和旋转的算法

func move(sprite: SKSpriteNode, velocity: CGPoint) {
    let amountToMove = CGPoint(x: velocity.x * CGFloat(dt), 
                               y: velocity.y * CGFloat(dt))
    sprite.position += amountToMove
  }

  func rotate(sprite: SKSpriteNode, direction: CGPoint, rotateRadiansPerSec: CGFloat) {
    let shortest = shortestAngleBetween(angle1: sprite.zRotation, angle2: velocity.angle)
    let amountToRotate = min(rotateRadiansPerSec * CGFloat(dt), abs(shortest))
    sprite.zRotation += shortest.sign() * amountToRotate
  }

Step14 边界检测

func boundsCheckZombie() {
    let bottomLeft = CGPoint(x: cameraRect.minX, y: cameraRect.minY)
    let topRight = CGPoint(x: cameraRect.maxX, y: cameraRect.maxY)

    if zombie.position.x <= bottomLeft.x {
      zombie.position.x = bottomLeft.x
      velocity.x = abs(velocity.x)
    }
    if zombie.position.x >= topRight.x {
      zombie.position.x = topRight.x
      velocity.x = -velocity.x
    }
    if zombie.position.y <= bottomLeft.y {
      zombie.position.y = bottomLeft.y
      velocity.y = -velocity.y
    }
    if zombie.position.y >= topRight.y {
      zombie.position.y = topRight.y
      velocity.y = -velocity.y
    } 
  }

Step15 猫的捕获方法

func moveTrain() {

    var trainCount = 0 //设置捕获猫的数量
    var targetPosition = zombie.position //保存僵尸的位置

    enumerateChildNodes(withName: "train") { node, stop in //遍历所有猫的节点
      trainCount += 1 //增加猫的捕获数
      if !node.hasActions() { //当猫失去了行动
        let actionDuration = 0.3 //行动时间
        let offset = targetPosition - node.position //进行猫和僵尸的偏移计算
        let direction = offset.normalized() //转换成速度(方向加距离)
        let amountToMovePerSec = direction * self.catMovePointsPerSec //每秒猫移动的距离
        let amountToMove = amountToMovePerSec * CGFloat(actionDuration) //总共移动的距离
        let moveAction = SKAction.moveBy(x: amountToMove.x, y: amountToMove.y, duration: actionDuration)
        node.run(moveAction) //让猫移动
      }
      targetPosition = node.position //重置目标位置为之前捕获猫的位置
    }

    if trainCount >= 15 && !gameOver { //捕获超过15只
      gameOver = true
      print("You win!")
      backgroundMusicPlayer.stop()

      // 1
      let gameOverScene = GameOverScene(size: size, won: true)
      gameOverScene.scaleMode = scaleMode
      // 2
      let reveal = SKTransition.flipHorizontal(withDuration: 0.5)
      // 3
      view?.presentScene(gameOverScene, transition: reveal) //切换场景
    }

    catsLabel.text = "Cats: \(trainCount)" //更新捕获数

  }

Step16 移动摄像头

func moveCamera() {
    let backgroundVelocity =
      CGPoint(x: cameraMovePointsPerSec, y: 0)
    let amountToMove = backgroundVelocity * CGFloat(dt)
    cameraNode.position += amountToMove //摄像头进行移动

    enumerateChildNodes(withName: "background") { node, _ in //遍历背景节点
      let background = node as! SKSpriteNode
      if background.position.x + background.size.width < 
          self.cameraRect.origin.x { //当触碰边界 向后移动背景的位置
        background.position = CGPoint(
          x: background.position.x + background.size.width*2,
          y: background.position.y)
      }
    }

  }

Step17 进行屏幕的点击操作

override func touchesBegan(_ touches: Set<UITouch>,
      with event: UIEvent?) {
    guard let touch = touches.first else {
      return
    }
    let touchLocation = touch.location(in: self)
    sceneTouched(touchLocation: touchLocation)
  }

  override func touchesMoved(_ touches: Set<UITouch>,
      with event: UIEvent?) {
    guard let touch = touches.first else {
      return
    }
    let touchLocation = touch.location(in: self)
    sceneTouched(touchLocation: touchLocation)
  }

  func sceneTouched(touchLocation:CGPoint) {
    lastTouchLocation = touchLocation
    moveZombieToward(location: touchLocation)
  }

func moveZombieToward(location: CGPoint) {
    startZombieAnimation()
    let offset = location - zombie.position
    let direction = offset.normalized()
    velocity = direction * zombieMovePointsPerSec //更新速度, update逐帧渲染
  }

Step18 进行僵尸动画

func startZombieAnimation() {
    if zombie.action(forKey: "animation") == nil {
      zombie.run(
        SKAction.repeatForever(zombieAnimation), //重复播放纹理动画
        withKey: "animation")
    }
  }

  func stopZombieAnimation() {
    zombie.removeAction(forKey: "animation") //删除行动
  }

Step19 碰撞检测

override func didEvaluateActions() { //update后调用
    checkCollisions()
  }

func checkCollisions() {
    var hitCats: [SKSpriteNode] = [] //捕获到猫的数组
    enumerateChildNodes(withName: "cat") { node, _ in //遍历所有的猫
      let cat = node as! SKSpriteNode
      if cat.frame.intersects(self.zombie.frame) { 
        hitCats.append(cat) //如果和僵尸有发生碰撞, 添加入捕获数组
      }
    }

    for cat in hitCats {
      zombieHit(cat: cat) //进行捕获操作
    }

    if invincible {
      return //如果僵尸处以无敌状态 不检测碰撞老太
    }

    var hitEnemies: [SKSpriteNode] = [] //被老太击倒数组
    enumerateChildNodes(withName: "enemy") { node, _ in //遍历所有的老太
      let enemy = node as! SKSpriteNode
      if node.frame.insetBy(dx: 20, dy: 20).intersects( //老太向内收缩触碰区域
        self.zombie.frame) {
        hitEnemies.append(enemy) //添加数组
      }
    }
    for enemy in hitEnemies {
      zombieHit(enemy: enemy) //碰撞老太
    }
  }

Step20 碰撞后的操作

func zombieHit(cat: SKSpriteNode) {
    cat.name = "train" //更改猫的标识, 标记为捕获
    cat.removeAllActions() //删除所有行动
    cat.setScale(1.0) //缩放至正常比率
    cat.zRotation = 0 //旋转至正常比率

    let turnGreen = SKAction.colorize(with: SKColor.green, colorBlendFactor: 1.0, duration: 0.2)
    cat.run(turnGreen) //改变颜色

    run(catCollisionSound) //播放音效
  }

  func zombieHit(enemy: SKSpriteNode) {
    invincible = true //设置为无敌状态
    let blinkTimes = 10.0 //闪烁时间
    let duration = 3.0 //无敌时间
    let blinkAction = SKAction.customAction(withDuration: duration) { node, elapsedTime in //
      let slice = duration / blinkTimes
      let remainder = Double(elapsedTime).truncatingRemainder(
        dividingBy: slice)
      node.isHidden = remainder > slice / 2
    }
    let setHidden = SKAction.run() { [weak self] in
      self?.zombie.isHidden = false
      self?.invincible = false
    }
    zombie.run(SKAction.sequence([blinkAction, setHidden])) //进行执行序列

    run(enemyCollisionSound) //播放音效

    loseCats() //丢失猫的操作
    lives -= 1 //失去生命值
  }

Step21 丢失猫的操作

func loseCats() {
    // 1
    var loseCount = 0 // 丢失数量
    enumerateChildNodes(withName: "train") { node, stop in //遍历已捕获的猫的节点
      // 2
      var randomSpot = node.position // 猫进行随机移动
      randomSpot.x += CGFloat.random(min: -100, max: 100)
      randomSpot.y += CGFloat.random(min: -100, max: 100)
      // 3
      node.name = "" //清空标识
      node.run(
        SKAction.sequence([
          SKAction.group([
            SKAction.rotate(byAngle: π*4, duration: 1.0),
            SKAction.move(to: randomSpot, duration: 1.0),
            SKAction.scale(to: 0, duration: 1.0)
            ]),
          SKAction.removeFromParent()
        ]))
      // 4
      loseCount += 1
      if loseCount >= 2 { //设置只丢失2只
        stop[0] = true
      }
    }
  }

Step22 游戏结束的场景

class GameOverScene: SKScene {  let won:Bool //是否胜利

  init(size: CGSize, won: Bool) {    self.won = won    super.init(size: size)
  }  required init(coder aDecoder: NSCoder) {    fatalError("init(coder:) has not been implemented")
  }  override func didMove(to view: SKView) {    var background: SKSpriteNode
    if (won) {
      background = SKSpriteNode(imageNamed: "YouWin") //胜利的图片及音效
      run(SKAction.playSoundFileNamed("win.wav", 
          waitForCompletion: false))
    } else {
      background = SKSpriteNode(imageNamed: "YouLose") //失败的图片及音效
      run(SKAction.playSoundFileNamed("lose.wav", 
          waitForCompletion: false))
    }

    background.position = 
      CGPoint(x: size.width/2, y: size.height/2)    self.addChild(background)    // More here...
    let wait = SKAction.wait(forDuration: 3.0) //等待3秒后重新开始游戏

    let block = SKAction.run {      let myScene = GameScene(size: self.size)
      myScene.scaleMode = self.scaleMode      let reveal = SKTransition.flipHorizontal(withDuration: 0.5)      self.view?.presentScene(myScene, transition: reveal)
    }    self.run(SKAction.sequence([wait, block]))

  }

}