viewpager2-cache-size.kt

class ChildFragment : Fragment() {
  private lateinit var binding: ChildFragBinding

  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View? {
    binding = ChildFragBinding.inflate(inflater, container, false)
    return binding.root
  }

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    binding.viewPager.isUserInputEnabled = false
    val adapter = ChildAdapter(this)
    binding.viewPager.adapter = adapter

    val childView = binding.viewPager[0] as RecyclerView
    childView.setItemViewCacheSize(5)
  }
}

class ChildAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {
  override fun getItemCount(): Int = 5

  override fun createFragment(position: Int): Fragment {
    return when (position % 5) {
      0 -> Child1Fragment()
      1 -> Child2Fragment()
      2 -> Child3Fragment()
      3 -> Child4Fragment()
      else -> Child5Fragment()
    }
  }
}