Paused layer come unpause after start app from background

Question

I have set play/pause button to gameLayer - here: How to prevent run SKAction on paused scene (after unpaused), texture of node not change after pause/unpause scene

Everything works fine, but I'm helpless with app on background. When I pause gameLayer and app goes to background or when I lock device, after app going to foreground, game layer is automatically unpause. How to prevent this?

Thanks!

Answer 1

So this is what worked for me:

import SpriteKit
import GameplayKit

class GameScene: SKScene {

    var gameLayer = SKNode()

    override func didMove(to view: SKView) {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(GameScene.pause),
                                               name: .UIApplicationDidBecomeActive,
                                               object: nil)
        let moveUp = SKAction.moveBy(x: 0, y: 100, duration: 2)
        let sequence = SKAction.sequence([moveUp, moveUp.reversed()])
        let loop = SKAction.repeatForever(sequence)

        let sprite = SKSpriteNode(color: .purple, size: CGSize(width: 100, height: 100))

        addChild(gameLayer)
        gameLayer.addChild(sprite)

        sprite.run(loop)
    }

    func pause(){

        gameLayer.speed = 0
    }

    override func willMove(from view: SKView) {
        super.willMove(from: view)

        NotificationCenter.default.removeObserver(self,
                                                  name: .UIApplicationDidBecomeActive,
                                                  object: nil)
    }

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

        gameLayer.speed = gameLayer.speed == 0 ? 1 : 0
    }
}

I haven't had time to test more, but I was expecting that something like this:

 func pause(){
        gameLayer.isPaused = true
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
       gameLayer.isPaused = !gameLayer.isPaused
    }

would work, but surprisingly it isn't (the node continued with moving after the pause() method was executed). I don't really know if this is a bug or a feature :) but IMHO, I would say it is a bug. Anyways, you can achieve what you want using the speed property. Just copy and paste this code to see how it works.