使用spritkit创建游戏暂停功能

Question

我使用spritkit创建一个比赛游戏

我创建按钮如果用户点击它然后它将暂停游戏，我的问题是场景停止移动但是汽车会像真车一样慢慢停止，我想停止没有重力

这是我的代码

    physicsWorld.gravity = CGVectorMake(0.0,0.3);
    physicsWorld.contactDelegate = self

这是播放器代码

        playerNode = SKSpriteNode(imageNamed: "car")
        playerNode!.position = CGPoint(x: size.width / 2.0, y: 120.0)
        playerNode!.physicsBody =
            SKPhysicsBody(circleOfRadius: playerNode!.size.width / 2)
        playerNode!.physicsBody!.dynamic = true
        playerNode!.physicsBody!.linearDamping = 1.0
        playerNode!.physicsBody!.allowsRotation = true
        playerNode!.physicsBody!.categoryBitMask = CollisionCategoryPlayer
        playerNode!.physicsBody!.contactTestBitMask =
        CollisionCategoryPowerUpOrbs
        playerNode!.physicsBody!.collisionBitMask = 0
        foregroundNode!.addChild(playerNode!)

最后这是暂停功能

 if (pasueornot){ // true or false
                physicsWorld.gravity = CGVectorMake(0.0,gravitySpeed)
            }
            else{
                physicsWorld.gravity = CGVectorMake(0.0,0.0) // the Scene stop from moving but the car will stop slowly like the real car pasueornot
            }