sprite-kit – 将背景颜色淡入另一种颜色的替代方法

red = starting_red * (1.0 - fraction) + ending_red * fraction
green = starting_green * (1.0 - fraction) + ending_green* fraction
blue = starting_blue * (1.0 - fraction) + ending_blue * fraction

分数从0开始,以1为增量结束于1

fraction += delta_time * step_size

实现此方法的一种方法是将代码添加到GameScene的didMoveToView方法中.但是,如果您的游戏包含多个场景,则更好的策略是扩展SKAction以添加创建自定义动作的类方法,以便所有场景都可以使用它.

首先,定义一个结构来存储起始和结束RGB颜色分量.在GameScene的定义之外添加它.

struct ColorComponents {
    var red:CGFloat
    var green:CGFloat
    var blue:CGFloat

    init(color:SKColor) {
        self.init()
        var alpha:CGFloat = 0
        color.getRed(&red,green: &green,blue: &blue,alpha: &alpha)
    }

    init() {
        red = 0
        green = 0
        blue = 0
    }
}

然后,通过添加以下方法来扩展SKAction,将背景颜色更改为另一种颜色.请注意,扩展必须在类之外定义.

extension SKAction {
    static func changeColor(startColor:SKColor,endColor:SKColor,duration:NSTimeInterval) -> SKAction {
        // Extract and store starting and ending colors' RGB components
        let start = ColorComponents(color: startColor)
        let end = ColorComponents(color: endColor)
        // Compute the step size
        let stepSize = CGFloat(1/duration)
        // Define a custom class to gradually change a scene's background color
        let change = SKAction.customActionWithDuration(duration) {
            node,time in
            let fraction = time * stepSize
            let red = start.red * (1.0 - fraction) + end.red * fraction
            let green = start.green * (1.0 - fraction) + end.green * fraction
            let blue = start.blue * (1.0 - fraction) + end.blue * fraction
            if let scene = node as? SKScene {
                scene.backgroundColor = SKColor(red: red,green: green,blue: blue,alpha: 1.0)
            }
        }
        return change
    }
}

最后,创建并运行SKAction

runAction(SKAction.changeColor(backgroundColor,endColor: SKColor.blueColor(),duration: 5))

将此添加到SKScene子类中的didMoveToView,例如GameScene.