尝试添加已经拥有父级的SKNode

Question

更新：

在我的帖子中，我认为这是一个导致崩溃的physicsBody属性错误，但事实并非如此。

当两个物体发生碰撞时，它应该结束游戏，并显示游戏结束屏幕。但是，在随机时间，应用程序将崩溃。我找不到它为什么会这样做的模式。有时它是第一次这样做，其他的，我可以在它崩溃应用程序之前多次重启。我收到错误：

'Attemped to add a SKNode which already has a parent: <GameOverLayer> name:'(null)' position:{0, 0} accumulatedFrame:{{0, 0}, {320, 568}}'

有问题的代码是此方法的最后一行：

- (void) showGameOverLayer
{
    //Remove currently exising on pillars from scene and purge them
    for (int i = self.children.count - 1; i >= 0; i--)
    {
        SKNode* childNode = [self.children objectAtIndex:i];

        if(childNode.physicsBody.categoryBitMask == pillerCategory)
        {
            [childNode removeAllActions];
        }
    }
    [_flappyBird removeAllActions];
    _flappyBird.physicsBody.velocity = CGVectorMake(0, 0);
    self.physicsWorld.gravity = CGVectorMake(0, 0.0);
    _flappyBird.hidden = YES;

    _gameOver = YES;
    _gameStarted = NO;

    _dt = 0;
    _lastUpdateTimeInterval = 0;
    _lastSpawnTimeInterval = 0;

    [_startGameLayer removeFromParent];
    [self addChild:_gameOverLayer];
}

我正在学习使用SpriteKit，我只是按照制作像Flappy Bird这样的游戏的教程，所以这对我来说都是比较新的。

显示_gameOverLayer removeFromParent部分的每个地方：

- (void) showStartGameLayer
{
    //Remove currently exising on pillars from scene and purge them
    for (int i = self.children.count - 1; i >= 0; i--)
    {
        SKNode* childNode = [self.children objectAtIndex:i];
        if(childNode.physicsBody.categoryBitMask == pillerCategory)
        {
            [childNode removeFromParent];
        }
    }

    //Move Flappy Bird node to center of the scene
    self.flappyBird.position = CGPointMake(self.backgroundImageNode.size.width * 0.5f, self.frame.size.height * 0.6f);

    [_gameOverLayer removeFromParent];

    _flappyBird.hidden = NO;
    [self flyingBird];
    [self addChild:_startGameLayer];
}

- (void) startGame
{
    _score = 0;

    _gameStarted = YES;

    [_startGameLayer removeFromParent];
    [_gameOverLayer removeFromParent];

    self.flappyBird.position = CGPointMake(self.backgroundImageNode.size.width * 0.3f, self.frame.size.height * 0.6f);

    //To have Gravity effect on Bird so that bird flys down when not tapped
    self.physicsWorld.gravity = CGVectorMake(0, -4.0);
}