This Adapter eliminates the need to write custom RecyclerView.Adapters

GeneralAdapter.kt

package com.mrezanasirloo.adapter

import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView

/**
 * This adapter eliminates the need to write custom [RecyclerView.Adapter]s and
 * [RecyclerView.ViewHolder]s by delegating the view holder creation and binding to the [Item] class
 */
class GeneralAdapter(
    private val items: List<Item>
) : RecyclerView.Adapter<ViewHolder>() {

    private var lastViewTypeLookup: Item? = null

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(itemViewType(viewType).onCreateView(parent))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        items[position].onBind(holder, position)
    }

    override fun onViewRecycled(holder: ViewHolder) {
        super.onViewRecycled(holder)
        holder.item?.unbind(holder)
    }

    override fun getItemViewType(position: Int): Int {
        /** Finds and holds a reference to the last view type requested to
         * eliminate viewType lookup time
         */
        lastViewTypeLookup = items.takeIf { position >= 0 && position < items.size }?.get(position)
        checkNotNull(lastViewTypeLookup) { "Invalid position $position" }
        return lastViewTypeLookup!!.viewType
    }

    /**
     * Returns the last viewType lookup otherwise finds it.
     * The last [lastViewTypeLookup] cannot be null it this point
     * The find mechanism is just a safeguard against future internal change of [RecyclerView.Adapter]
     */
    private fun itemViewType(viewType: Int): Item {
        return lastViewTypeLookup?.takeIf { it.viewType == viewType }
            ?: items.find { it.viewType == viewType }
            ?: throw IllegalStateException("Could not find item for viewType: $viewType")
    }

    override fun getItemCount(): Int = items.size
}

Item.kt

package com.mrezanasirloo.adapter

import android.view.View

/**
 * Extend this class to show different type of Items inside a [GeneralAdapter]
 */
abstract class Item {

    open val viewType: Int = javaClass.hashCode()

    abstract fun onCreateView(parent: View): View

    open fun onBind(holder: ViewHolder, position: Int) {}

    open fun onUnbind(holder: ViewHolder) {}

    internal fun bind(holder: ViewHolder, position: Int) {
        holder.bind(this)
        onBind(holder, position)
    }

    internal fun unbind(holder: ViewHolder) {
        holder.unbind()
        onUnbind(holder)
    }
}

ViewHolder.kt

package com.mrezanasirloo.adapter

import android.view.View
import androidx.recyclerview.widget.RecyclerView

/**
 * Holds a reference to an [Item] until its [unbind]
 */
class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {

    internal var item: Item? = null
        private set

    internal fun bind(item: Item) {
        this.item = item
    }

    internal fun unbind() {
        item = null
    }
}