Kotlin ListAdapter With DiffUtils

WordDetailAdapterKotlin.kt

package sharif.vocapower.ui.adapter

import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.*
import kotlinx.android.synthetic.main.item_primary_word_list.view.*
import kotlinx.android.synthetic.main.list_item_mnemonic.view.*
import sharif.vocapower.R
import sharif.vocapower.data.db.entity.Mnemonic
import sharif.vocapower.data.db.entity.Word

class WordDetailAdapterKotlin : ListAdapter<Word, WordDetailAdapterKotlin.ViewHolder>(WordNameDiffCallback()) {

    private var mnemonics: List<Mnemonic>? = ArrayList()
    private var mCurrentPosition : Int = 0

    fun addMnemonic(mnemonicList: List<Mnemonic>, position: Int){
        mCurrentPosition = position
        mnemonics = mnemonicList
        notifyItemChanged(position)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val inflater = LayoutInflater.from(parent.context)
        return ViewHolder(inflater.inflate(R.layout.item_primary_word_list, parent, false))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(getItem(position), mnemonics)
    }

    inner class ViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView) {
        private var mnemonicAdapterKotlin = MnemonicAdapterKotlin()
        init {
            itemView.rv_mnemonic.setHasFixedSize(true)
            itemView.rv_mnemonic.itemAnimator = DefaultItemAnimator()
            itemView.rv_mnemonic.layoutManager = LinearLayoutManager(itemView.context)
            itemView.rv_mnemonic.adapter = mnemonicAdapterKotlin
        }

        fun bind(word: Word, mnemonics: List<Mnemonic>?) {
            Log.d("TEC", "adapter position $adapterPosition and current position $mCurrentPosition")
            itemView.tv_word.text = word.name
            itemView.tv_meaning.text = word.meaning
            itemView.tv_bangla_meaning.text = word.meaningBangla
            itemView.tv_hindi_meaning.text = word.meaningHindi
            if (adapterPosition == mCurrentPosition){
                mnemonicAdapterKotlin.submitList(mnemonics)
            }else{

            }

        }
    }

    class WordNameDiffCallback : DiffUtil.ItemCallback<Word>() {
        override fun areItemsTheSame(oldItem: Word, newItem: Word): Boolean {
            return oldItem.name == newItem.name
        }

        override fun areContentsTheSame(oldItem: Word, newItem: Word): Boolean {
            return oldItem.name == newItem.name && oldItem.isFavorite == newItem.isFavorite
        }
    }
}

class MnemonicAdapterKotlin : ListAdapter<Mnemonic, MnemonicAdapterKotlin.ViewHolder>(MnemonicDiffUtilCallback()){

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val inflater = LayoutInflater.from(parent.context)
        return MnemonicAdapterKotlin.ViewHolder(inflater.inflate(R.layout.list_item_mnemonic, parent, false))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(getItem(position))
    }

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun bind(mnemonic: Mnemonic?) {
            itemView.tv_mnemonic.text = mnemonic?.mnemonic
            ///itemView.tv_mnemonic_user.text = "By " + mnemonic?.uname
        }
    }

    class MnemonicDiffUtilCallback : DiffUtil.ItemCallback<Mnemonic>() {
        override fun areItemsTheSame(oldItem: Mnemonic, newItem: Mnemonic): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: Mnemonic, newItem: Mnemonic): Boolean {
            return oldItem.mnemonic == newItem.mnemonic
        }

    }

}