How can I display Recycler view in Fragment?

class UserFragment : Fragment() {

    var fragmentView: View? = null

    var firestore: FirebaseFirestore? = null
    var currentUserUid: String? = null 
    var uid: String? = null /
    var auth: FirebaseAuth? = = null

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        currentUserUid = FirebaseAuth.getInstance().currentUser?.uid
        auth = FirebaseAuth.getInstance()
        uid = arguments?.getString("destinationUid")
        firestore = FirebaseFirestore.getInstance()


        fragmentView = inflater.inflate(R.layout.fragment_user, container, false)

        return fragmentView
    }


//Apply viewpager adapter
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        user_content_viewpager.adapter = UserMainAdapter
        user_content_viewpager.offscreenPageLimit = 1

        setOnClickListener()


    }

    <-- setOnClickListener omitted -->

}

class ViewplantsFragment : Fragment() {
    var fragmentplantsView: View? = null
    var firestore: FirebaseFirestore? = null
    var uid: String? = null 
    var auth: FirebaseAuth? = = null

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {

        firestore = FirebaseFirestore.getInstance()
        uid = UserFragment().arguments?.getString("destinationUid")
        auth = FirebaseAuth.getInstance()


        fragmentplantsView = inflater.inflate(R.layout.fragment_viewplants, container, false)
        fragmentplantsView?.user_viewplants_recyclerview?.layoutManager = GridLayoutManager(activity!!, 3)
        fragmentplantsView?.user_viewplants_recyclerview?.adapter = ViewplantsFragmentRecyclerViewAdapter()

        return fragmentplantsView
    }

//Code for displaying recyclerview in this fragment
    inner class ViewplantsFragmentRecyclerViewAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

        //import from database
        var contentDTOs: ArrayList<ContentDTO>

        init {
            contentDTOs = ArrayList()
            firestore?.collection("images")?.whereEqualTo("uid", uid)
                ?.addSnapshotListener { querySnapshot, firebaseFirestoreException ->
                    if (querySnapshot == null) return@addSnapshotListener
                    for (snapshot in querySnapshot.documents) {
                        contentDTOs.add(snapshot.toObject(ContentDTO::class.java)!!)
                    }

                    //Post Counter Count
                    UserFragment().user_plants_count.text = contentDTOs.size.toString()
                    notifyDataSetChanged()
                }
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {


            var width = resources.displayMetrics.widthPixels / 3 //Divided to match screen resolution
            var imageview = ImageView(parent.context)
            imageview.layoutParams = LinearLayoutCompat.LayoutParams(width, width)

            return CustomViewHolder(imageview)
        }


        private inner class CustomViewHolder(var imageview: ImageView) : RecyclerView.ViewHolder(imageview) {
        }

        override fun getItemCount(): Int {
            return contentDTOs.size
        }

        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
            var imageview = (holder as CustomViewHolder).imageview
            Glide.with(holder.itemView.context).load(contentDTOs[position].imageUrl)
                .apply(RequestOptions().centerCrop()).into(imageview)
        }

    }
}

class MainActivity : AppCompatActivity() ,BottomNavigationView.OnNavigationItemSelectedListener {

    override fun onNavigationItemSelected(item: MenuItem): Boolean {


        when (item.itemId) {

            <--Middle omitted-->

            R.id.action_mypage -> {
                my_toolbar.visibility = View.GONE

                var userFragment = UserFragment()

                var bundle = Bundle()
                var uid = FirebaseAuth.getInstance().currentUser?.uid
                bundle.putString("destinationUid",uid) //Apply user uid
                userFragment.arguments = bundle

                supportFragmentManager.beginTransaction().replace(R.id.main_content, userFragment).commit()


                return true
            }

        }
        return false
    }

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

        main_bottom_navigation.setOnNavigationItemSelectedListener(this)

        //Authorize Photo Storage
        ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.READ_EXTERNAL_STORAGE), 1)

        main_bottom_navigation.selectedItemId = R.id.action_home


    }