sample.kt

class EventFragment {

    companion object {
        var fragmentEventsView : FragmentEventsView? = null

        fun register(fragmentEventsView: FragmentEventsView) {
            this.fragmentEventsView = fragmentEventsView
        }

        fun unRegister() {
            this.fragmentEventsView = null
        }

        fun emitterUpdateUI(position: Int) {
            if (this.fragmentEventsView != null) {
                this.fragmentEventsView!!.onUpdateUI(position)
            }
        }
    }

    interface FragmentEventsView {
        fun onUpdateUI(position: Int)
    }

}

in fragment

class BlankFragment : Fragment() {

    private lateinit var view : View
    
    private val currentPosition = 2

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        view =  inflater.inflate(R.layout.fragment_blank, container, false)
        EventFragment.register(object : EventFragment.FragmentEventsView {
            override fun onUpdateUI(position: Int) {
                if (position == currentPosition) {
                    if(isVisible) {
                        presenter.findOne(App.token, App.credentialId)
                    }
                }
            }
        })
        return view
    }

    override fun onDestroy() {
        super.onDestroy()
        EventFragment.unRegister()
    }
}

in viewpager

navigationTabBar.setOnPageChangeListener(object : ViewPager.OnPageChangeListener {
    override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
    }

    override fun onPageSelected(position: Int) {
       EventFragment.emitterUpdateUI(position)
    }

    override fun onPageScrollStateChanged(state: Int) {
    }
})