Customizing NavigationBar per XLPagerTabStrip ButtonBarPagerTabStripViewController page

I am using XLPagerTabStrip library and using the ButtonBarPagerTabStripViewController. This is what the hierarchy looks like:

The ButtonBarPagerTabStripViewController is embedded inside a navigationController and I have two different viewControllers that the ButtonBarPagerTabStripViewController contains. The problem is that I want to change how the navigationBar looks based one either ViewController1 or ViewController2.

For example, when the tab is one viewController1, I want to have a barButton "+". For viewController2, I want to have a barButton of report. However, I cannot make modifications to the navigationController bar from viewController1 and viewController2.

Is there a way?

ButtonBarPagerTabStripViewController class has a override function to handle this.

override func updateIndicator(for viewController: PagerTabStripViewController, fromIndex: Int, toIndex: Int, withProgressPercentage progressPercentage: CGFloat, indexWasChanged: Bool) {
    if progressPercentage == 1 {
        // Add `+` button to navigation item
    } else {
        // Add `report` button to navigation item
    }
}

Add condition as per your total number of view controllers on the screen.

Update

Please see the below code used in the demo project.

import UIKit
import XLPagerTabStrip

class MainTabBarViewController: ButtonBarPagerTabStripViewController {

    var isFirstView: Bool = true
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    func getSegmentList() -> [UIViewController] {
        let firstViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "FirstViewController")
        firstViewController.title = "First"
        let secondViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "SecondViewController")
        secondViewController.title = "Second"
        return [firstViewController, secondViewController]
    }
    
    func setUI() {
        let addImage = UIImage(systemName: "plus")
        let addBarButton = UIBarButtonItem(image: addImage, style: .plain, target: self, action: #selector(addButtonAction(_:)))
        let reportImage = UIImage(systemName: "book")
        let reportBarButton = UIBarButtonItem(image: reportImage, style: .plain, target: self, action: #selector(reportButtonAction(_:)))
        navigationItem.rightBarButtonItem = isFirstView ? addBarButton : reportBarButton
    }
    
    @IBAction func addButtonAction(_ sender: UIBarButtonItem) {
        print("Add button action")
        // Add button action
    }
    
    @IBAction func reportButtonAction(_ sender: UIBarButtonItem) {
        print("Report button action")
        // Report button action
    }
    
    override func viewControllers(for pagerTabStripController: PagerTabStripViewController) -> [UIViewController] {
        return getSegmentList()
    }
    
    override func updateIndicator(for viewController: PagerTabStripViewController, fromIndex: Int, toIndex: Int, withProgressPercentage progressPercentage: CGFloat, indexWasChanged: Bool) {
        if progressPercentage == 1 {
            let viewController = viewController.viewControllers[toIndex] as? FirstViewController
            isFirstView = viewController?.title == "First"
            setUI()
        }
    }

}

Output: