sprite-kit - SpriteKit : How to identify the previous scene the user is coming from?

Question

我有一个 GameOver 场景，其中包含一个指向“设置”场景的按钮。 (下面显示的代码)我想在 MainMenu 场景上添加一个按钮来执行相同的操作，将用户发送到 Settings 场景，但我只想在 Settings 场景上添加一个“后退”按钮。我假设这可以通过 IF 语句来完成。如果用户来自 A 场景则移动到 B 否则如果用户来自 X 场景则移动到 Y 场景。

我如何在 SpriteKit 中判断用户来自哪个场景？

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

    for touch: AnyObject in touches {

        let pointOfTouch = touch.location(in: self)

        let nodeUserTapped = atPoint(pointOfTouch)

        if nodeUserTapped.name == "BackButton" {

            let sceneToMoveTo = SKScene(fileNamed: "GameOverScene")
            let gameTransition = SKTransition.fade(withDuration: 0.5)
            self.view!.presentScene(sceneToMoveTo!, transition: gameTransition)

        }

    }

}

Answer 1

在这种情况下，您可以采用各种解决方案来实现您的愿望。我只想向您展示 2 个示例，一种是快速简单的方法，另一种是更自定义的方法。

---

1: - 您可以使用 userData下一个场景的实例属性来存储当前场景，例如:

sceneToMoveTo.userData = NSMutableDictionary()
sceneToMoveTo.userData?.setObject("MenuScene", forKey: "previousScene" as NSCopying)

当你在下一个场景时，你可以问这个 NSMutableDictionary 谁是前一个场景:

guard let previousValue = self.userData?.value(forKey: "previousScene") else { return }
switch previousValue as! String {
case "MenuScene":
   //do whatever you want if the previous scene was MenuScene
default:
   break
}

---

2: - 您可以构建一个枚举，其中包含您要移动到的场景列表。

之后，每个场景都包含一个简单的 var 来存储前一个场景:默认为 .None 但您应该在调用新场景时填充它。当您到达 SettingsScene 并按下后退按钮时，您可以询问这个 previousScene var 谁是前一个场景，并通过 switch 语句决定去哪里。

// GAMEOVER SCENE
import SpriteKit
enum Scenes : Int {
    case MainMenu = 0
    case Settings = 1
    case GameOver = 2
    case None = 3
}
class GameOver: SKScene {
    var previousScene:Scenes = .None
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch: AnyObject in touches {
            let pointOfTouch = touch.location(in: self)
            let nodeUserTapped = atPoint(pointOfTouch)
            if nodeUserTapped.name == "settingsBtn" {
                if let sceneToMoveTo = SKScene(fileNamed: "SettingsScene") {
                    let gameTransition = SKTransition.fade(withDuration: 0.5)
                    (sceneToMoveTo as! SettingsScene).previousScene = .GameOver
                    self.view?.presentScene(sceneToMoveTo, transition: gameTransition)
                }   
            }     
        }
    }
}
// SETTINGS SCENE
import SpriteKit
class SettingsScene: SKScene {
    var previousScene:Scenes = .None
    override func didMove(to view: SKView) {
        print("Current scene loaded: \(type(of:self))")
        print("Previous scene was: \(previousScene)")
        let label = SKLabelNode.init(text: "BackButton")
        addChild(label)
        label.position = CGPoint(x:self.frame.midX,y:self.frame.midY)
        label.name = "backBtn"
    }
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch: AnyObject in touches {
            let pointOfTouch = touch.location(in: self)
            let nodeUserTapped = atPoint(pointOfTouch)
            if nodeUserTapped.name == "backBtn" {
                switch previousScene {
                case .MainMenu: // go back to menu
                    if let sceneToMoveTo = SKScene(fileNamed: "MenuScene") {
                        let gameTransition = SKTransition.fade(withDuration: 0.5)
                        (sceneToMoveTo as! MenuScene).previousScene = .Settings
                        self.view?.presentScene(sceneToMoveTo, transition: gameTransition)
                    }
                    break
                case .GameOver: // re-launch a new game
                    print("The game was ended")
                    if let sceneToMoveTo = SKScene(fileNamed: "GameScene") {
                        let gameTransition = SKTransition.fade(withDuration: 0.5)
                        (sceneToMoveTo as! GameScene).previousScene = .Settings
                        self.view?.presentScene(sceneToMoveTo, transition: gameTransition)
                    }
                default:
                    break
                }
            }

        }
    }
}
//MENU SCENE
import SpriteKit
class MenuScene: SKScene {
    var previousScene:Scenes = .None
    override func didMove(to view: SKView) {
        print("Current scene loaded: \(type(of:self))")
        print("Previous scene was: \(previousScene)")
    }
}