XLPagerTabStrip ButtonBar sticks behind Navigation Bar

I'm using XLPagerTabStrip in a swift 3 application, I use the default ButtonBar and everything works fine but the bar is hidden when I have a navigation bar enabled like this:

If I hide the navigation bar, it shows like this:

How do I get it below the navigation bar not behind it, because I need the navigation bar right there?

import UIKit
import XLPagerTabStrip

class DesignersController: ButtonBarPagerTabStripViewController {

override func viewDidLoad() {

    buttonBarView.backgroundColor = .white
    settings.style.buttonBarBackgroundColor = .white
    settings.style.selectedBarBackgroundColor = UIColor(netHex: 0x4a4a4a)
    settings.style.selectedBarHeight = 1
    settings.style.buttonBarItemBackgroundColor = .white
    settings.style.buttonBarItemTitleColor = UIColor(netHex: 0x8c8c8c)

    super.viewDidLoad()
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    self.navigationController?.setNavigationBarHidden(true, animated: animated)
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    //self.navigationController?.setNavigationBarHidden(false, animated: animated)
}

var isReload = false

override func viewControllers(for pagerTabStripController: PagerTabStripViewController) -> [UIViewController] {
    let child_1 = ChildExampleViewController(itemInfo: "Top")
    let child_2 = ChildExampleViewController(itemInfo: "Men")
    let child_3 = ChildExampleViewController(itemInfo: "Women")

    guard isReload else {
        return [child_1, child_2, child_3]
    }

    var childViewControllers = [child_1, child_2, child_3]

    for (index, _) in childViewControllers.enumerated(){
        let nElements = childViewControllers.count - index
        let n = (Int(arc4random()) % nElements) + index
        if n != index{
            swap(&childViewControllers[index], &childViewControllers[n])
        }
    }
    let nItems = 1 + (arc4random() % 8)
    return Array(childViewControllers.prefix(Int(nItems)))
}

override func reloadPagerTabStripView() {
    isReload = true
    if arc4random() % 2 == 0 {
        pagerBehaviour = .progressive(skipIntermediateViewControllers: arc4random() % 2 == 0, elasticIndicatorLimit: arc4random() % 2 == 0 )
    }
    else {
        pagerBehaviour = .common(skipIntermediateViewControllers: arc4random() % 2 == 0)
    }
    super.reloadPagerTabStripView()
}
}


import Foundation
import XLPagerTabStrip

class ChildExampleViewController: UIViewController, IndicatorInfoProvider {

var itemInfo: IndicatorInfo = "View"

init(itemInfo: IndicatorInfo) {
    self.itemInfo = itemInfo
    super.init(nibName: nil, bundle: nil)
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

override func viewDidLoad() {
    super.viewDidLoad()

    let label = UILabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    label.text = "XLPagerTabStrip"

    view.addSubview(label)
    view.backgroundColor = .red

    view.addConstraint(NSLayoutConstraint(item: label, attribute: .centerX, relatedBy: .equal, toItem: view, attribute: .centerX, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: label, attribute: .centerY, relatedBy: .equal, toItem: view, attribute: .centerY, multiplier: 1, constant: -50))
}

// MARK: - IndicatorInfoProvider

func indicatorInfo(for pagerTabStripController: PagerTabStripViewController) -> IndicatorInfo {
    return itemInfo
}
}

Thanks in advance.

I just faced the same problem. Just add a CollectionView to VC in Interface Builder, and set its class to "ButtonBarView".Here Then connect its outlet with view in left panel.Like this Thats all, now buttonBar should be under NavigationBar.