func addBlurEffect() {
    // Add blur view
    let bounds = self.navigationController?.navigationBar.bounds as CGRect!
    let visualEffectView = UIVisualEffectView(effect: UIBlurEffect(style: .light))
    visualEffectView.frame = bounds!
    visualEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    self.navigationController?.navigationBar.addSubview(visualEffectView)
    self.navigationController?.navigationBar.sendSubview(toBack: visualEffectView)
    visualEffectView.isUserInteractionEnabled = false
}

bounds.offsetBy(dx: 0.0, dy: -20.0)
bounds.size.height = bounds.height + 20.0

[[UINavigationBar appearance] setBackgroundImage:[[UIImage alloc]init] forBarMetrics:UIBarMetricsDefault];
[[UINavigationBar appearance] setShadowImage:[[UIImage alloc]init]];
[[UINavigationBar appearance] setBackgroundColor:[UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.0f]];
[[UINavigationBar appearance] setTranslucent:YES];