How to rotate sprite in sprite kit with swift

问题

Hi my problem is regarding the rotation of two sprites. When I touch the right half of the screen the rotation starts and moving sprite2 and sprite3. If I touch the left half of the screen the rotation stops because velocity-velocity = 0. If I touch the left half again the rotation begins.

However, if I touch the half of the screen corresponding with the current rotational-direction the velocity is duplicated. I want to be able to change the direction of the rotation, but for the speed to remain constant.

Video demonstrating the problem: http://youtu.be/HxLwl1QZiNM

import SpriteKit

class GameScene: SKScene {
    let sprite = SKSpriteNode(imageNamed:"bWhite")
    let sprite2 = SKSpriteNode(imageNamed:"bBlue")
    let sprite3 = SKSpriteNode(imageNamed:"bRed")
    let circle = SKSpriteNode(imageNamed:"bCircle")       

    override func didMoveToView(view: SKView) {
        /* Setup your scene here */
        backColor = SKColor(red: 0, green: 0, blue: 0, alpha: 1)
        self.backgroundColor = backColor

        sprite.setScale(1.25)
        sprite2.setScale(1)
        sprite3.setScale(1)
        sprite.position = CGPointMake(self.frame.size.width/2, (self.frame.size.height/2)-200);
        circle.position = CGPointMake(self.frame.size.width/2, (self.frame.size.height/2)-200);
        sprite3.zRotation = 172.77
        sprite2.anchorPoint = CGPointMake(-1.10, 0.5);
        sprite3.anchorPoint = CGPointMake(-1.10, 0.5);

        self.addChild(sprite)
        self.addChild(circle)
        sprite.addChild(sprite2)
        sprite.addChild(sprite3)
    }

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
        /* Called when a touch begins */
        for touch: AnyObject in touches {
            let location = touch.locationInNode(self)

            let action = SKAction.rotateByAngle(CGFloat(M_PI), duration:1)
            let action2 = SKAction.rotateByAngle(CGFloat(-M_PI), duration:1)

            if (location.x > self.frame.size.width / 2)
            {
                sprite2.runAction(SKAction.repeatActionForever(action2))
                sprite3.runAction(SKAction.repeatActionForever(action2))
            } else {
                sprite2.runAction(SKAction.repeatActionForever(action))
                sprite3.runAction(SKAction.repeatActionForever(action))
            }     
        }
    }

回答1:

OK, take three. I'm not 100% sure about the specifics of when the rotation should end etc. but all the pieces should be in place with the below code. It will:

start rotation clockwise or counterclockwise based on the position of the first touch
stop the rotation if the user touches for the same direction again

switch the rotation if the user touches on the other half of the screen

  import SpriteKit  

  enum rotationDirection{
       case clockwise
       case counterClockwise
       case none
   } 

  class GameScene: SKScene {
    var currentRotationDirection = rotationDirection.none
    let sprite = SKSpriteNode(color: UIColor.yellowColor(), size: CGSizeMake(100, 100))

    override func didMoveToView(view: SKView) {
      sprite.physicsBody = SKPhysicsBody(rectangleOfSize: sprite.size)
      sprite.physicsBody.affectedByGravity = false
      sprite.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame))
      self.addChild(sprite)
    }

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
      let touch : UITouch = touches.anyObject() as UITouch
      let touchPosition = touch.locationInNode(self)
      let newRotationDirection : rotationDirection = touchPosition.x < CGRectGetMidX(self.frame) ? .clockwise : .counterClockwise

      if currentRotationDirection != newRotationDirection && currentRotationDirection != .none{
        reverseRotation()
        currentRotationDirection = newRotationDirection
      } else if currentRotationDirection == newRotationDirection{
        stopRotation()
        currentRotationDirection = .none
      } else if (currentRotationDirection == .none){
      setupRotationWith(direction: newRotationDirection)
      currentRotationDirection = newRotationDirection
      }
    }

    func reverseRotation(){
      let oldRotateAction = sprite.actionForKey("rotate")
      let newRotateAction = SKAction.reversedAction(oldRotateAction)
      sprite.runAction(newRotateAction(), withKey: "rotate")
    }

    func stopRotation(){
      sprite.removeActionForKey("rotate")
    }

    func setupRotationWith(#direction: rotationDirection){
      let angle : Float = (direction == .clockwise) ? Float(M_PI) : -Float(M_PI)
      let rotate = SKAction.rotateByAngle(angle, duration: 1)
      let repeatAction = SKAction.repeatActionForever(rotate)
      sprite.runAction(repeatAction, withKey: "rotate")
    }
  }

Edit: Changed example to cater the specific needs in the question. Something odd with the code formatting not quite sure what's going on there.

回答2:

I suggest removing all current actions before adding new, since they may conflict. I'm still not sure what you are trying to achieve, can you explain more?

回答3:

Have you just tired removing the actions at touchesEnded? I had a similar problem before where I wanted my object to move left to right based on which half of the screen the user touched. I had a similar issue where if I touched right and right again my velocity would double, and if I touched left my object would just stop.

I fixed this issue by adding the touchesEnded method and just removed the actions whenever I let go. This essentially reset my move action so the object would stop when I let go and would go to the opposite direction right away instead of having to tap it twice.

来源：https://stackoverflow.com/questions/24239271/how-to-rotate-sprite-in-sprite-kit-with-swift

标签

ios

rotation

sprite-kit

swift

ios8