Screenshots on Device vs Simulator

问题

Why would does this work on simulator but not on a device.

I am trying to capture a screenshot of a view that contains more than one AVPlayer.I can snap a frame from a player, but I need the actual screenshot as the view contains a few players, in specific locations on the screen at once.

There are multiple threads regarding this topic, but I am yet to find an answer.

- (UIImage *) takeScreenShot
{
    UIImage *image;
    CGSize snapArea = self.view.bounds.size;
    int bottomTobBarHeight = 44;
    snapArea.height = snapArea.height - bottomTobBarHeight;
    UIGraphicsBeginImageContextWithOptions(snapArea, YES, 1.0);
    [self.view drawViewHierarchyInRect:self.view.bounds afterScreenUpdates:YES];
    image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

来源：https://stackoverflow.com/questions/22681147/screenshots-on-device-vs-simulator