如何根据速度为精灵设置动画？

Question

嘿，我有一个项目，其中玩家应该像 Mega Jump 一样向上，我想为玩家设置动画，以便当它向左或向右或向下移动时，它会根据它改变其图像。有什么想法可以实现这一目标吗？这是我创建播放器的代码。

class GameScene: SKScene, SKPhysicsContactDelegate  {

let foregroundNode = SKNode()
let player = SKNode()

override init(size: CGSize) {
    super.init(size: size)

    physicsWorld.gravity = CGVector(dx: 0.0, dy: -3.0)
    physicsWorld.contactDelegate = self

    foregroundNode = SKNode()
    addChild(foregroundNode)

    player = createPlayer()
    foregroundNode.addChild(player)
}

func createPlayer() -> SKNode {

    let playerNode = SKNode()
    playerNode.position = CGPoint(x: self.size.width / 2, y: 80.0)
    var spriteTexture = SKTexture(imageNamed: "IMAGE")
    var sprite = SKSpriteNode(texture: spriteTexture)
    playerNode.addChild(sprite)

    playerNode.physicsBody = SKPhysicsBody(circleOfRadius: sprite.size.width / 2)
    playerNode.physicsBody?.dynamic = false
    playerNode.physicsBody?.allowsRotation = false
    playerNode.physicsBody?.restitution = 1.0
    playerNode.physicsBody?.friction = 0.0
    playerNode.physicsBody?.angularDamping = 0.0
    playerNode.physicsBody?.linearDamping = 0.0
    playerNode.physicsBody?.usesPreciseCollisionDetection = true
    playerNode.physicsBody?.categoryBitMask = CollisionCategoryBitmask.Player
    playerNode.physicsBody?.collisionBitMask = 0
    playerNode.physicsBody?.contactTestBitMask = CollisionCategoryBitmask.Star | CollisionCategoryBitmask.Platform | CollisionCategoryBitmask.Monster
    return playerNode
}

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
    if player.physicsBody!.dynamic {
        return
    }
    tapToStartNode.removeFromParent()
    player.physicsBody?.dynamic = true
    player.physicsBody?.applyImpulse(CGVector(dx: 0.0, dy: 30.0))

}

override func update(currentTime: NSTimeInterval) {

    var spriteTexture = SKTexture(imageNamed: "IMAGE")
    var sprite = SKSpriteNode(texture: spriteTexture)
    if (player.physicsBody?.velocity.dx < 0) && (player.physicsBody?.velocity.dy > 0) {

        sprite.texture = SKTexture(imageNamed: "IMAGE LEFT")


    } else if (player.physicsBody?.velocity.dx > 0) && (player.physicsBody?.velocity.dy > 0){

        sprite.texture = SKTexture(imageNamed: "IMAGE RIGHT")

    }

我不知道我是走在正轨还是做错了，我还在学习 sprite kit 和 swift。但是，如果有人可以帮助我实现这一目标，我将不胜感激！提前谢谢你

Answer 1

如果您打算为图像制作动画，则不应直接使用图像制作精灵节点。相反，使用 Image 的名称初始化 SKTexture。现在，您可以使用该纹理制作您的精灵节点。从那时起，只需使用纹理，因为每个精灵节点都有一个您可以直接设置的texture 属性 - sprite.texture。

Answer 2

你会在你的更新方法中这样做：

Update()
{
    if(player.velocity.dx < 0 && sprite.texture != self.rightTexture)
          sprite.texture = self.rightTexture;
    else if(player.velocity.dx > 0 && sprite.texture != self.leftTexture)
          sprite.texture = self.leftTexture;
    //Add checks for down or up.  Order it based on what takes priority.

}

此代码遍历每一帧并根据其速度更新您的纹理。在开始时加载纹理并重复使用它们以节省内存和性能。