实现‘点击恢复’功能-Tap-to-ResumeFeatureinSpriteKit

虽然SpriteKit框架已经具备了当应用进入非活动状态时自动暂停游戏的功能，但有时我们可能需要在应用恢复活跃状态时向用户显示一个‘点击恢复’的提示。当前，尽管我的游戏能够正确响应并暂停，但这个提示文字却没有显示出来。

为了实现这一功能，我在AppDelegate.swift文件中添加了相应的通知处理器，用于在应用即将变为非活跃状态时发送暂停游戏的通知，并在应用恢复活跃状态时显示‘点击恢复’的提示。

AppDelegate.swift

func applicationWillResignActive(_ application: UIApplication) {
    // 当应用即将从活跃状态变为非活跃状态时调用。这可能是由于临时中断（如来电或短信）或用户退出应用导致。
    print("applicationWillResignActive")
    NotificationCenter.default.post(name: Notification.Name("PauseGameScene"), object: nil)
    NotificationCenter.default.post(name: Notification.Name("ShowPauseText"), object: nil)
}

GameScene.swift

class GameScene: SKScene, SKPhysicsContactDelegate {
    private let tapToResume = SKLabelNode(fontNamed: "Noteworthy")

    override func didMove(to view: SKView) {
        NotificationCenter.default.addObserver(self, selector: #selector(pauseGameScene), name: Notification.Name("PauseGameScene"), object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(showPauseText), name: Notification.Name("ShowPauseText"), object: nil)

        tapToResume.text = "tap to resume"
        tapToResume.position = CGPoint(x: frame.midX, y: frame.midY)
        tapToResume.fOntSize= 55
        tapToResume.isHidden = true
        addChild(tapToResume)
    }

    @objc func pauseGameScene() {
        print("Pausing game")
        view?.isPaused = true
    }

    @objc func showPauseText() {
        if view?.isPaused == true {
            tapToResume.isHidden = false
            print("Showing pause text")
        }
    }

    override func touchesBegan(_ touches: Set, with event: UIEvent?) {
        if isPaused {
            view?.isPaused = false
            if !tapToResume.isHidden {
                tapToResume.isHidden = true
            }
        }
    }
}

在尝试解决这个问题的过程中，我发现了一个有效的解决方案。通过将self.speed和self.physicsWorld.speed都设置为0.0，不仅可以暂停所有动作，还可以使物理世界停止更新。当应用再次激活时，只需将这两个属性重置为1.0即可恢复正常游戏状态。

改进后的GameScene.swift

class GameScene: SKScene, SKPhysicsContactDelegate {
    private let tapToResume = SKLabelNode(fontNamed: "Noteworthy")

    override func didMove(to view: SKView) {
        NotificationCenter.default.addObserver(self, selector: #selector(pauseGameScene), name: Notification.Name("PauseGameScene"), object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(showPauseText), name: Notification.Name("ShowPauseText"), object: nil)
    }

    @objc func pauseGameScene() {
        physicsWorld.speed = 0.0
        speed = 0.0
    }

    @objc func showPauseText() {
        if physicsWorld.speed == 0.0 {
            tapToResume.isHidden = false
        }
    }

    override func touchesBegan(_ touches: Set, with event: UIEvent?) {
        if physicsWorld.speed == 0.0 {
            physicsWorld.speed = 1.0
            speed = 1.0
            if !tapToResume.isHidden {
                tapToResume.isHidden = true
            }
        }
    }
}

改进后的AppDelegate.swift

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    func applicationWillResignActive(_ application: UIApplication) {
        NotificationCenter.default.post(name: Notification.Name("PauseGameScene"), object: nil)
        NotificationCenter.default.post(name: Notification.Name("ShowPauseText"), object: nil)
    }
}