UIkit elements can't see in overlaySKScene for AR.

Hi.

I making some simple AR app with interfaces using overlaySKScene.

In viewDidLoad, I applied overlay scene in main ARSCNView(OverlayScene is my class inherited SKScene).

self.sceneView.overlaySKScene = [[OverlayScene alloc] initWithSize:self.sceneView.bounds.size];
self.sceneView.overlaySKScene.delegate = self;

Then, I added UIkit button in OverlayScene init.

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 200, 100)];
[button setTitle:@"button" forState:UIControlStateNormal];
button.layer.position = CGPointMake(self.view.frame.size.width/2, 200);
[self.view addSubview:button];

But, that button didn't appear on screen.

When I added sprite node in this scene, it worked.

Is there other method for it or bug?

Thank you.