MultiViewTypeAdapter

ExampleAdapter.kt

package com.tonyjs.sample.multiviewtypeadapter.kotlin

import kotlinx.android.synthetic.main.item_a.view.*

/**
 * Created by tonyjs on 2017. 4. 2..
 */
class ExampleAdapter : MultiViewTypeAdapter() {

    companion object {
        const val VIEW_TYPE_DIVIDER = 0
        const val VIEW_TYPE_A = 1
        const val VIEW_TYPE_B = 2
        const val VIEW_TYPE_C = 3
    }

    override fun registerBinders() {
        register<String>(VIEW_TYPE_A, R.layout.item_a, { holder, item ->
            holder.itemView.tvTitle.text = item
        })
        register<String>(VIEW_TYPE_B, R.layout.item_b, { holder, item ->
            holder.itemView.tvTitle.text = item
        })
        register<String>(VIEW_TYPE_C, R.layout.item_c, { holder, item ->
            holder.itemView.tvTitle.text = item
        })
        register<Float>(VIEW_TYPE_DIVIDER, R.layout.item_divider, { _, _ ->
        })
    }

    override fun getViewType(position: Int): Int {
        if (items[position] is Float) {
            return VIEW_TYPE_DIVIDER
        }
        return when (position % 3) {
            1 -> VIEW_TYPE_B
            2 -> VIEW_TYPE_C
            else -> VIEW_TYPE_A
        }
    }

}

MultiViewTypeAdapter.kt

package com.tonyjs.sample.multiviewtypeadapter.kotlin

import android.support.annotation.LayoutRes
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup

/**
 * Created by tonyjs on 2017. 4. 2..
 */
abstract class MultiViewTypeAdapter : RecyclerView.Adapter<MultiViewTypeAdapter.ViewHolder>() {

    open val items = mutableListOf<Any>()

    val binderMap = hashMapOf<Int, Binder>()

    fun <ITEM> register(viewType: Int, @LayoutRes layoutRes: Int,
                        binder: (holder: ViewHolder, ITEM) -> Unit) {
        binderMap.put(viewType, object : Binder {
            override val layoutResId: Int
                get() = layoutRes

            @Suppress("UNCHECKED_CAST")
            override fun <T> bind(holder: ViewHolder, item: T) {
                binder(holder, item as ITEM)
            }
        })
    }

    abstract fun registerBinders()

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val resId = binderMap[viewType]?.layoutResId ?:
                throw NullPointerException("require layout resource id")
        val itemView = LayoutInflater.from(parent.context).inflate(resId, parent, false)
        return ViewHolder(itemView)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val viewType = getItemViewType(position)
        binderMap[viewType]?.bind(holder, items[position])
    }

    override fun getItemViewType(position: Int): Int {
        if (binderMap.isEmpty()) {
            registerBinders()
        }
        return getViewType(position)
    }

    abstract fun getViewType(position: Int): Int

    override fun getItemCount(): Int = items.size

    inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view)

    interface Binder {

        @get:LayoutRes
        val layoutResId: Int

        fun <T> bind(holder: ViewHolder, item: T)

    }

}