试试，不要用viewDidLoad，用这个

- (void)viewWillLayoutSubviews
{
    [super viewWillLayoutSubviews];

    SKView * skView = (SKView *)self.view;
    if (!skView.scene) {
        skView.showsFPS = YES;
        skView.showsNodeCount = YES;

        SKScene * scene = [MyScene sceneWithSize:skView.bounds.size];
        scene.scaleMode = SKSceneScaleModeAspectFill;

        // Present the scene.
        [skView presentScene:scene];
    }
}