kotlin fragment error NullPointerException - android-fragments

Question

my complete code
class BlankFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val rootView = inflater.inflate(R.layout.mainex, container, false)
val groupAdapter = GroupAdapter<ViewHolder>().apply {
spanCount = 2
}
recycler_view.apply {
//error NullPointerException in this line
layoutManager = GridLayoutManager(rootView.context, groupAdapter.spanCount).apply {
spanSizeLookup = groupAdapter.spanSizeLookup
}
adapter = groupAdapter
}
var headerTab: ArrayList<mTop>
headerTab = arguments?.getSerializable("headertab") as ArrayList<mTop>
for (h in 0 until headerTab.size) {
val header = headerTab.get(h).kategori
ExpandableGroup(ExpandableHeaderItem(header), true).apply {
for (c in 0 until headerTab[h].sub.size) {
val gambar = (headerTab[h].sub).get(c).gambar
val nama_menu = (headerTab[h].sub).get(c).nama_menu
add(Section(FancyItem(gambar, nama_menu)))
}
groupAdapter.add(this)
}
}
I'm trying to make the recyclerview display in the tablayout fragment
and an error occurred, maybe the problem comes from rootView.context
layoutManager = GridLayoutManager(rootView.context, groupAdapter.spanCount).apply {
spanSizeLookup = groupAdapter.spanSizeLookup
}
thanks :) (sorry, my english is bad)

Answer 1

You are setting LayoutManager to recyclerView before the view is created. You should do this in onViewCreated() method or in the xml file. Use onCreateView() only for inflating the view. And then use onViewCreated() for others settings you need to do to your views.

Answer 2

Done. this my complete fix code with separate onCreateView and onViewCreate. thanks all
class FragBaru : Fragment() {
private lateinit var rv: RecyclerView
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.mainex, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
rv = view.findViewById(R.id.recycler_view)
val groupAdapter = GroupAdapter<ViewHolder>().apply {
spanCount = 2
}
rv.apply {
layoutManager = GridLayoutManager(rootView.context, groupAdapter.spanCount).apply {
spanSizeLookup = groupAdapter.spanSizeLookup
}
adapter = groupAdapter
}
var headerTab: ArrayList<mTop>
headerTab = arguments?.getSerializable("headertab") as ArrayList<mTop>
for (h in 0 until headerTab.size) {
val header = headerTab.get(h).kategori
ExpandableGroup(ExpandableHeaderItem(header), true).apply {
for (c in 0 until headerTab[h].sub.size) {
val gambar = (headerTab[h].sub).get(c).gambar
val nama_menu = (headerTab[h].sub).get(c).nama_menu
add(Section(FancyItem(gambar, nama_menu)))
}
groupAdapter.add(this)
}
}
}
companion object {
fun newInstance(headertab: ArrayList<mTop>): FragBaru {
val f = FragBaru()
val args = Bundle()
args.putSerializable("headertab", headertab)
f.setArguments(args)
return f
}
}
}