I don't know how to use currnet item in viewpager - kotlin

Question

I want to use currentItem on Fragments in viewpager2
ViewPager is also fragment. and my all fragments have viewbinding.
My fragment call viewpager by findViewById. But It isn't worked. It's data is always 'null'. Can I use findviewbyid and viewbinding both of them? I already tried to use findViewbyID in onviewcreated or oncreateview Please help me
pagertest.kt(first page fragment)
class pagertest : Fragment() {
private var _binding: FragmentPagertestBinding? = null
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
_binding = FragmentPagertestBinding.inflate(inflater, container, false)
binding.button5.setOnClickListener {
val pager = activity?.findViewById<ViewPager2>(R.id.dayspager22)
pager?.currentItem = 2
}
return binding.root
}
}
dayspager22.kt(ViewPagerFragment)
class dayspager22 : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
private var _binding: FragmentDayspager22Binding? = null
private val binding get() = _binding!!
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentDayspager22Binding.inflate(inflater, container, false)
val fragmentList = arrayListOf<Fragment>(
pagertest(),
days_1(),
days_2(),
days_3()
)
val adapter = ViewPagerAdapter(
fragmentList,
requireActivity().supportFragmentManager,
lifecycle
)
binding.views.adapter = adapter
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment dayspager22.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic
fun newInstance(param1: String, param2: String) =
dayspager22().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}
ViewPage Adapter
class ViewPagerAdapter(
list: ArrayList<Fragment>,
fm: FragmentManager,
lifecycle: Lifecycle
) : FragmentStateAdapter(fm, lifecycle) {
private val fragmentList = list
override fun getItemCount(): Int {
return fragmentList.size
}
override fun createFragment(position: Int): Fragment {
return fragmentList[position]
}
}

Answer 1

I think it might be because you're creating and adding pagertest to the adapter inside dayspager22's onCreateView method. You haven't returned its layout view yet, so it's not added to the Activity's layout - and if it's not added, you won't be able to find it with findViewById. (I'm not sure exactly when pagertest's onCreateView runs here, but I'd look into that possibility.)
Also make sure fragment_dayspager_22.xml or whatever actually has a ViewPager2 with an id of dayspager22 - you're setting your adapter on something called views:
val adapter = ViewPagerAdapter(
fragmentList,
requireActivity().supportFragmentManager,
lifecycle
)
// you're setting a ViewPagerAdapter on something that's probably a ViewPager,
// and its id is R.id.views
binding.views.adapter = adapter
Are you sure that's not the ID you want to look up with findViewById?