使用精灵套件垂直滚动背景的问题

Question

我正在尝试垂直滚动游戏背景，它可以工作一段时间，后来背景变空。这是我尝试过的：

var background = SKSpriteNode(imageNamed: "bgPlayScene")

func addBG() {

    let backgroundTexture = SKTexture(imageNamed: "bgPlayScene")

    let shiftBackground = SKAction.moveToY(-backgroundTexture.size().height, duration: 9)
    let replaceBackground = SKAction.moveToY(backgroundTexture.size().height, duration: 0)
    let movingAndReplacingBackground = SKAction.repeatActionForever(SKAction.sequence([shiftBackground,replaceBackground]))

    for var i = 0; i<3; i++ {
        println(i)
        //defining background; giving it height and moving width
        background=SKSpriteNode(texture:backgroundTexture)
        background.position = CGPoint(x: self.size.width/2, y: self.size.height/2)
        background.size.width = self.frame.width
        background.runAction(movingAndReplacingBackground)

        self.addChild(background)
    }
}

这就是我得到的：http://gyazo.com/3da3a267aeb030225fdb8c0d563276aa 我不知道我错过了什么。如果有其他更好的方法，请告诉我。

Answer 1

正如iAnum 所建议的那样，我从post 得到了答案，这是我的代码：

这样我添加了 2 个背景。

func addScrollingBG() {

    bg1 = SKSpriteNode(imageNamed: "bgPlayScene")
    bg1.anchorPoint = CGPointZero
    bg1.position = CGPointMake(0, 0)
    bg1.size = CGSize(width: frame.size.width, height: frame.size.height)
    addChild(bg1)

    bg2 = SKSpriteNode(imageNamed: "bgPlayScene")
    bg2.anchorPoint = CGPointZero
    bg2.position = CGPointMake(0, bg1.size.height + 1)
    bg2.size = CGSize(width: frame.size.width, height: frame.size.height)
    self.addChild(bg2)

}

这是我的更新方法：

override func update(currentTime: NSTimeInterval) {

    bg1.position = CGPointMake(bg1.position.x, bg1.position.y-4)
    bg2.position = CGPointMake(bg2.position.x, bg2.position.y-4)

    if bg1.position.y < -bg1.size.height {
        bg1.position = CGPointMake(bg1.position.x, bg2.position.y + bg2.size.height)
    }
    if bg2.position.y < -bg2.size.height {
        bg2.position = CGPointMake(bg2.position.x, bg1.position.y + bg1.size.height)
    }
}