ios - 以一定速度在屏幕上随机移动物体

Question

我需要让我的对象在屏幕上随机移动。当它们移动时，该对象正在寻找一定半径范围内的另一个对象。

我找到了下面的链接，并实现了 getDuration 函数。但是我遇到了与主题所有者相同的故障。我可以看到应该可以通过删除运行操作来修复。

Moving an object across the screen at a certain speed.(Sprite Kit)

视频:https://www.youtube.com/watch?v=jHE5RC-mvwU

但是我现在已经试了好几种方案了，还是不行。当我停止 Action 时，我的对象就会停止移动。

有人可以告诉我，在哪里终止我的 Action ，在 moveToWaypoint 中创建？我需要我的对象移动到一个随机的路径点，但如果一个特定的对象进入半径内，那么它应该为壁橱对象设置一个新的路径点并再次开始操作。

代码:

///Called in update method
func move(scene: GameplayScene) {
    checkForWaypoint()
    checkForFood(scene: scene)
    moveToWaypoint()
}

///Creates a new waypoint
func createWaypoint() {
     waypoint = CGPoint(x: randomBetweenNumbers(firstNum: minX, secondNum: maxX), y: randomBetweenNumbers(firstNum: minX, secondNum: maxX))
}

override func checkForFood(scene: GameplayScene) {
    var closesObject: SKNode? = nil

    scene.enumerateChildNodes(withName: "Food") {
        node, _ in
        let distance = node.position.distanceFromCGPoint(point: self.position)

        if distance < self.FOOD_RANGE  {
            closesObject = node
        }
    }

    if hungryState == HungryState.hungry {
        if closesObject != nil {
            waypoint = closesObject?.position
            moveState = MoveState.movingToFood
        } else {
            if moveState == MoveState.movingToFood {
                createWaypoint()
            }
        }
    }
}

///Moves the object to the waypoint
func moveToWaypoint () {
    let action = SKAction.move(to: waypoint!, duration: getDuration(pointA: position, pointB: waypoint!, speed: 25))
    self.run(action)
}

///Calcuate a speed between to cordinates
private func getDuration(pointA:CGPoint,pointB:CGPoint,speed:CGFloat)-> TimeInterval {
    let xDist = (pointB.x - pointA.x)
    let yDist = (pointB.y - pointA.y)
    let distance = sqrt((xDist * xDist) + (yDist * yDist));
    let duration : TimeInterval = TimeInterval(distance/speed)
    return duration
}

编辑:

Gamescene 类的更新函数

override func update(_ currentTime: TimeInterval) {
    moveFish()
}

private func moveFish() {
    for node in self.children {
        if node.name != nil {
            switch node.name {
            case "Fish"?:
                let fishToMove = node as! Fish

                fishToMove.move(scene: self)

            default:
                break
            }
        }
    }
}

Answer 1

您在这里尝试解决的问题可以通过两种方式完成。首先是使用物理学，其次当然是没有它。我决定不学习物理，因为这显然是您的做法。

简而言之，这些示例中的鱼在周围没有食物时使用 SKAction 移动。当食物在范围内时，鱼会使用 update: 方法移动到它们的目标。当鱼吃掉它的发现物时，它会继续使用 SKAction 移动。

此外，在这之前，这里有一些我从 Stackoverflow 借来的有用的扩展，您将来可能会发现它们很有用:

import SpriteKit
import GameplayKit

//Extension borrowed from here : https://stackoverflow.com/a/40810305
extension ClosedRange where Bound : FloatingPoint {
    public func random() -> Bound {
        let range = self.upperBound - self.lowerBound
        let randomValue = (Bound(arc4random_uniform(UINT32_MAX)) / Bound(UINT32_MAX)) * range + self.lowerBound
        return randomValue
    }
}
//Extension borrowed from here : https://stackoverflow.com/a/37760551
extension CGRect {
    func randomPoint() -> CGPoint {
        let origin = self.origin
        return CGPoint(x:CGFloat(arc4random_uniform(UInt32(self.width))) + origin.x,
                       y:CGFloat(arc4random_uniform(UInt32(self.height))) + origin.y)
    }
}

//Extension borrowed from here:  https://stackoverflow.com/a/33292919

extension CGPoint {
    func distance(point: CGPoint) -> CGFloat {
        return abs(CGFloat(hypotf(Float(point.x - x), Float(point.y - y))))
    }
}

现在有一个像您这样的 Fish 类，它只有很少的方法和一个物理体，仅用于检测食物和鱼之间的接触，但那都是来自物理学的。这是 Collider 结构，以防您想知道我是如何定义它的:

struct Collider{
            static let food : UInt32 = 0x1 << 0
            static let fish : UInt32 = 0x1 << 1
            static let wall : UInt32 = 0x1 << 2
        }

现在回到 Fish 类...我已经在代码中添加了注释，所以我想不需要解释这些方法的作用。这是代码:

class Fish:SKSpriteNode{
    private let kMovingAroundKey = "movingAround"
    private let kFishSpeed:CGFloat = 4.5
    private var swimmingSpeed:CGFloat = 100.0
    private let sensorRadius:CGFloat = 100.0
    private weak var food:SKSpriteNode! = nil //the food node that this fish currently chase

    override init(texture: SKTexture?, color: UIColor, size: CGSize) {
        super.init(texture: texture, color: color, size: size)

        physicsBody = SKPhysicsBody(rectangleOf: size)
        physicsBody?.affectedByGravity = false
        physicsBody?.categoryBitMask = Collider.fish
        physicsBody?.contactTestBitMask = Collider.food
        physicsBody?.collisionBitMask = 0x0 //No collisions with fish, only contact detection
        name = "fish"

        let sensor = SKShapeNode(circleOfRadius: 100)
        sensor.fillColor = .red
        sensor.zPosition = -1
        sensor.alpha = 0.1
        addChild(sensor)
    }

    func getDistanceFromFood()->CGFloat? {


        if let food = self.food {

            return self.position.distance(point: food.position)
        }
        return nil

    }

    func lock(food:SKSpriteNode){

        //We are chasing a food node at the moment
        if let currentDistanceFromFood = self.getDistanceFromFood() {

            if (currentDistanceFromFood > self.position.distance(point: food.position)){
                //chase the closer food node
                 self.food = food
                self.stopMovingAround()
            }//else, continue chasing the last locked food node

        //We are not chasing the food node at the moment
        }else{
             //go and chase then
             if food.position.distance(point: self.position) <= self.sensorRadius {

                self.food = food
                self.stopMovingAround()
            }
        }
    }

    //Helper method. Not used currently. You can use this method to prevent chasing another (say closer) food while already chasing one
    func isChasing(food:SKSpriteNode)->Bool{

        if self.food != nil {

            if self.food == food {
                return true
            }
        }

        return false
    }

    func stopMovingAround(){

        if self.action(forKey: kMovingAroundKey) != nil{
           removeAction(forKey: kMovingAroundKey)
        }
    }


    //MARK: Chasing the food
    //This method is called many times in a second
    func chase(within rect:CGRect){

        guard let food = self.food else {

            if action(forKey: kMovingAroundKey) == nil {
                self.moveAround(within: rect)
            }
            return
        }

        //Check if food is in the water
        if rect.contains(food.frame.origin) {

            //Take a detailed look in my Stackoverflow answer of how chasing works : https://stackoverflow.com/a/36235426

            let dx = food.position.x - self.position.x
            let dy = food.position.y - self.position.y

            let angle = atan2(dy, dx)

            let vx = cos(angle) * kFishSpeed
            let vy = sin(angle) * kFishSpeed

            position.x += vx
            position.y += vy

        }
    }

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

    func moveAround(within rect:CGRect){

        if scene != nil {

            //Go randomly around the screen within view bounds
            let point = rect.randomPoint()

            //Formula: time = distance / speed
            let duration = TimeInterval(point.distance(point: position) / self.swimmingSpeed)
            let move = SKAction.move(to: point, duration: duration)
            let block = SKAction.run {
                [unowned self] in

                self.moveAround(within: rect)
            }
            let loop = SKAction.sequence([move,block])

            run(loop, withKey: kMovingAroundKey)
        }
    }
}

所以基本上，有一些方法可以在鱼不追逐食物的时候四处移动。还有一种方法可以停止这个(无限) Action (SKAction)。最重要的方法是 chase(within rect:) 方法。该方法在场景的 update() 方法中调用，并定义鱼将如何以及何时(尝试)追逐食物。

现在是 GameScene:

//MARK: GameScene
class GameScene: SKScene, SKPhysicsContactDelegate {

    private var nodesForRemoval:[SKNode] = []
    private var water = SKSpriteNode()

    override func didMove(to view: SKView) {

        physicsWorld.contactDelegate = self
        physicsWorld.gravity = CGVector(dx: 0.0, dy: -0.5)
        physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
        physicsBody?.categoryBitMask = Collider.wall
        physicsBody?.contactTestBitMask = 0x0
        physicsBody?.collisionBitMask = Collider.fish | Collider.food
        self.backgroundColor = .white

        //Water setup
        water = SKSpriteNode(color: .blue, size: CGSize(width: frame.width, height: frame.height - 150))
        water.position = CGPoint(x: 0, y: -75)
        water.alpha = 0.3
        addChild(water)
        water.zPosition = 4

        //Fish one
        let fish = Fish(texture: nil, color: .black, size:CGSize(width: 20, height: 20))
        addChild(fish)
        fish.position = CGPoint(x: frame.midX-50, y: frame.minY + 100)
        fish.zPosition = 5

        fish.moveAround(within: water.frame)

        //Fish two
        let fish2 = Fish(texture: nil, color: .black, size:CGSize(width: 20, height: 20))
        addChild(fish2)
        fish2.position = CGPoint(x: frame.midX+50, y: frame.minY + 100)
        fish2.zPosition = 5

        fish2.moveAround(within: water.frame)

    }


    func feed(at position:CGPoint, with food:SKSpriteNode){

        food.position = CGPoint(x: position.x, y: frame.size.height/2 - food.frame.size.height)
        addChild(food)
    }

    //MARK: Food factory :)
    func getFood()->SKSpriteNode{

        let food = SKSpriteNode(color: .purple, size: CGSize(width: 10, height: 10))

        food.physicsBody = SKPhysicsBody(rectangleOf: food.frame.size)
        food.physicsBody?.affectedByGravity = true
        food.physicsBody?.categoryBitMask = Collider.food
        food.physicsBody?.contactTestBitMask =  Collider.fish
        food.physicsBody?.collisionBitMask = Collider.wall
        food.physicsBody?.linearDamping = (0.1 ... 0.95).random()
        food.name = "food"
        return food
    }

    //MARK: Feeding
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

        if let touch = touches.first {

            let location = touch.location(in: self)

            let food = getFood()
            feed(at: location, with: food)
        }
    }

    //MARK: Eating
    func didBegin(_ contact: SKPhysicsContact) {


        guard let nodeA = contact.bodyA.node, let nodeB = contact.bodyB.node else {

            //Silliness like removing a node from a node tree before physics simulation is done will trigger this error
            fatalError("Physics body without its node detected!")
        }

        let mask = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask

        switch mask {

           //Contact between fish and a food
          case Collider.fish | Collider.food:

            if let food = (contact.bodyA.categoryBitMask == Collider.food ? nodeA : nodeB) as? SKSpriteNode
            {
                self.nodesForRemoval.append(food)
            }

        default:
            //some unknown contact occurred
            break
        }
    }

    //MARK: Removing unneeded nodes
    override func didSimulatePhysics() {

        for node in self.nodesForRemoval {
            node.removeFromParent()
        }
        self.nodesForRemoval.removeAll()
    }

    //MARK: Chasing the food
    override func update(_ currentTime: TimeInterval) {

        self.enumerateChildNodes(withName: "fish") {
            [unowned self] node, stop in

            if let fish = node as? Fish {

                self.enumerateChildNodes(withName: "food") {
                    node, stop in

                    fish.lock(food: node as! SKSpriteNode)
                }

                fish.chase(within: self.water.frame)
            }
        }
    }
}

就是这样。在这里，我们设置我们的节点，解决接触检测并告诉哪些鱼应该追逐哪个食物节点。我留下了评论，所以一切都在那里。我希望这些方法几乎是不言自明的，但是您当然可以向我询问有关其工作原理的详细信息。

这里是一个简短的视频，展示了它是如何工作的:

和更长的版本，因为我只能上传两个 2 兆字节:screen recording

基本上，如果食物节点不在它定义的范围内，鱼是不会追逐它的。尽管如此，鱼还是会追逐锁定的节点，直到它吃掉为止。但如果附近有其他食物，鱼就会追逐那个食物节点。当然这不是必须的，您可以根据需要调整它(检查 isChasing:)方法。