Activity that uses AppIntro Slidrs

WelcomeActivity.kt

package com.example.introsliders

import android.content.Intent
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import com.github.paolorotolo.appintro.AppIntro
import com.github.paolorotolo.appintro.AppIntro2Fragment
import com.github.paolorotolo.appintro.model.SliderPage
import com.github.paolorotolo.appintro.model.SliderPagerBuilder

class WelcomeActivity : AppIntro() {

    private lateinit var manager: PreferencesManager

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        manager = PreferencesManager(this)
        if (manager.isFirstRun()) {
            showIntroSlides()
        } else {
            goToMain()
        }
    }

    private fun showIntroSlides() {
        manager.setFirstRun()
        val pageOne = SliderPagerBuilder()
            .title(getString(R.string.slide_one_top_text))
            .description(getString(R.string.slide_one_down_text))
            .imageDrawable(R.drawable.logo)
            .bgColor(getColor(R.color.slide_one))
            .build()

        val pageTwo = SliderPagerBuilder()
            .title(getString(R.string.slide_two_top_text))
            .description(getString(R.string.slide_two_down_text))
            .imageDrawable(R.drawable.notebook_with_logo)
            .bgColor(getColor(R.color.slide_two))
            .build()

        val pageThree = SliderPagerBuilder()
            .title(getString(R.string.slide_three_top_text))
            .description(getString(R.string.slide_three_down_text))
            .imageDrawable(R.drawable.bow_classic_brown)
            .bgColor(getColor(R.color.slide_three))
            .build()

        val pageFour = SliderPagerBuilder()
            .title(getString(R.string.slide_four_top_text))
            .description(getString(R.string.slide_four_down_text))
            .imageDrawable(R.drawable.taget_and_arrow)
            .bgColor(getColor(R.color.slide_four))
            .build()

        addSlide(AppIntro2Fragment.newInstance(pageOne))
        addSlide(AppIntro2Fragment.newInstance(pageTwo))
        addSlide(AppIntro2Fragment.newInstance(pageThree))
        addSlide(AppIntro2Fragment.newInstance(pageFour))

        showStatusBar(false)
        setFadeAnimation()
    }

    private fun goToMain() {
        startActivity(Intent(this, MainActivity::class.java))
    }

    override fun onSkipPressed(currentFragment: Fragment?) {
        super.onSkipPressed(currentFragment)
        goToMain()
    }

    override fun onDonePressed(currentFragment: Fragment?) {
        super.onDonePressed(currentFragment)
        goToMain()
    }

    override fun onSlideChanged(oldFragment: Fragment?, newFragment: Fragment?) {
        super.onSlideChanged(oldFragment, newFragment)
        Log.d("Hello", "Changed")
    }
}

I think for your code to work, WelcomeActivity needs to be the launch activity in the manifest. It will work fine but it's not the recommended way in the official docs here : https://github.com/AppIntro/AppIntro#basic-usage (last paragraph). I, find it a bit of a waste to make WelcomeActivity as the launch activity knowing that it will be only true the first time.
Honestly I couldn't find a better way to manage this. I kept the main activity as a launch activity as recommended in the docs like this :

    override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       manager = PreferencesManager(this)
       if (manager.isFirstRun()) {
          manager.setFirstRun()
          val i = Intent(applicationContext, IntroActivity::class.java)
          startActivity(i)
      }
      setContentView(R.layout.activity_main)
    }

Works fine but that's not optimal because, while being on the first intro screen, clicking on the android back button will skip to the main activity instead of doing nothing. Putting setContentView(R.layout.activity_main) in an else block does not run any of the two activities and I do not know exactly why.

So, I could not find the perfect solution to satisfies everything.