How to Implement Tabs, ViewPager and Fragment in Android using Kotlin?

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment

// Here ":" symbol is indicate that LoginFragment
// is child class of Fragment Class
class LoginFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(
            R.layout.layout_login, container, false
        )
    }
    // Here "layout_login" is a name of layout file
    // created for LoginFragment
}

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment

// Here ":" symbol is indicate that SignupFragment
// is child class of Fragment Class
class SignupFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(
            R.layout.layout_signup, container, false
        )
    }
    // Here "layout_signup" is a name of layout file
    // created for SignFragment
}

import android.os.Bundle
import androidx.annotation.Nullable
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.Toolbar
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager
import androidx.fragment.app.FragmentPagerAdapter
import androidx.viewpager.widget.ViewPager
import com.google.android.material.tabs.TabLayout

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Create the object of Toolbar, ViewPager and 
        // TabLayout and use “findViewById()” method*/
        var tab_toolbar = findViewById<Toolbar>(R.id.toolbar)
        var tab_viewpager = findViewById<ViewPager>(R.id.tab_viewpager)
        var tab_tablayout = findViewById<TabLayout>(R.id.tab_tablayout)

        // As we set NoActionBar as theme to this activity 
        // so when we run this project then this activity doesn't 
        // show title. And for this reason, we need to run 
        // setSupportActionBar method
        setSupportActionBar(tab_toolbar)
        setupViewPager(tab_viewpager)

        // If we dont use setupWithViewPager() method then 
        // tabs are not used or shown when activity opened
        tab_tablayout.setupWithViewPager(tab_viewpager)
    }

    // This function is used to add items in arraylist and assign 
    // the adapter to view pager
    private fun setupViewPager(viewpager: ViewPager) {
        var adapter: ViewPagerAdapter = ViewPagerAdapter(supportFragmentManager)

        // LoginFragment is the name of Fragment and the Login 
        // is a title of tab
        adapter.addFragment(LoginFragment(), "Login")
        adapter.addFragment(SignupFragment(), "Signup")

        // setting adapter to view pager.
        viewpager.setAdapter(adapter)
    }

    // This "ViewPagerAdapter" class overrides functions which are 
    // necessary to get information about which item is selected 
    // by user, what is title for selected item and so on.*/
    class ViewPagerAdapter : FragmentPagerAdapter {

        // objects of arraylist. One is of Fragment type and 
        // another one is of String type.*/
        private final var fragmentList1: ArrayList<Fragment> = ArrayList()
        private final var fragmentTitleList1: ArrayList<String> = ArrayList()

        // this is a secondary constructor of ViewPagerAdapter class.
        public constructor(supportFragmentManager: FragmentManager)
                : super(supportFragmentManager)

        // returns which item is selected from arraylist of fragments.
        override fun getItem(position: Int): Fragment {
            return fragmentList1.get(position)
        }

        // returns which item is selected from arraylist of titles.
        @Nullable
        override fun getPageTitle(position: Int): CharSequence {
            return fragmentTitleList1.get(position)
        }

        // returns the number of items present in arraylist.
        override fun getCount(): Int {
            return fragmentList1.size
        }

        // this function adds the fragment and title in 2 separate  arraylist.
        fun addFragment(fragment: Fragment, title: String) {
            fragmentList1.add(fragment)
            fragmentTitleList1.add(title)
        }
    }
}