UIView to UIImage on Apple TV

hi all, i'm trying to capture a screen shot, so i wrote a UIView extension that renders itself to UIImage like that:

extension UIView {
  func toImage() -> UIImage {
    UIGraphicsBeginImageContextWithOptions(bounds.size, false, 0.0)
    drawViewHierarchyInRect(bounds, afterScreenUpdates: false)
    let img = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return img
  }
}

It seems worked on apple tv simulator but its not working on device.

What is the trick of the rendering a UIView to UIImage or capturing screen and returning as UIImage on tvOS different from iOS ?

Thanks.