DjakaTechnology

interface AdapterDelegate <T> {
    fun isForViewType(items: List<T>, position: Int): Boolean

    fun onCreateViewHolder(parent: ViewGroup): RecyclerView.ViewHolder

    fun onBindViewHolder(items: List<T>, position: Int, holder: RecyclerView.ViewHolder)
}

DjakaTechnology

class AdapterDelegateManager<T> {

    private val delegates = mutableListOf<AdapterDelegate<T>>()

    fun addDelegate(delegate: AdapterDelegate<T>) {
        delegates.add(delegate)
    }

    fun getItemViewType(items: List<T>, position: Int): Int {
        delegates.forEachIndexed { index, it ->  if (it.isForViewType(items, position)) return index }

DjakaTechnology

class GenericAdapter<T>(var items: List<T>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private val delegateManager = AdapterDelegateManager<T>()

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

    override fun getItemCount(): Int {
        return items.size

DjakaTechnology

class FeedAdapterOld(var items: List<FeedItem> = listOf()) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    override fun getItemViewType(position: Int): Int {
        return when(items[position]) {
            is FeedPostItem -> ITEM_POST_ID
            is FeedStandardItem -> ITEM_STANDARD_ID
            is FeedStoryItem -> ITEM_STORY_ID
            else -> -1
        }
    }

DjakaTechnology

class FeedAdapterOld(var items: List<FeedItem> = listOf()) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    override fun getItemViewType(position: Int): Int {
        return when(items[position]) {
            is FeedPostItem -> ITEM_POST_ID
            is FeedStandardItem -> ITEM_STANDARD_ID
            else -> -1
        }
    }

DjakaTechnology

class FeedPostAdapterDelegate : AdapterDelegate<FeedItem> {
    override fun isForViewType(items: List<FeedItem>, position: Int): Boolean {
        return items[position] is FeedPostItem
    }

    override fun onCreateViewHolder(parent: ViewGroup): RecyclerView.ViewHolder {
        return ItemPostViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.feed_post_item, parent, false)
        )
    }

DjakaTechnology

class FeedStandardAdapterDelegate : AdapterDelegate<FeedItem> {
    override fun isForViewType(items: List<FeedItem>, position: Int): Boolean {
        return items[position] is FeedStandardItem
    }

    override fun onCreateViewHolder(parent: ViewGroup): RecyclerView.ViewHolder {
        return ItemStandardViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.feed_standard_item, parent, false)
        )
    }

DjakaTechnology

class FeedStoryAdapterDelegate : AdapterDelegate<FeedItem> {
    override fun isForViewType(items: List<FeedItem>, position: Int): Boolean {
        return items[position] is FeedStoryItem
    }

    override fun onCreateViewHolder(parent: ViewGroup): RecyclerView.ViewHolder {
        return ItemStoryViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.feed_story_item, parent, false))
    }

    override fun onBindViewHolder(items: List<FeedItem>, position: Int, holder: RecyclerView.ViewHolder) {

DjakaTechnology

//If you dont want to use GenericAdapter
class FeedAdapter(var items: List<FeedItem>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private val delegateManager = AdapterDelegateManager<FeedItem>()

    init {
        delegateManager.run {
            addDelegate(FeedPostAdapterDelegate())
            addDelegate(FeedStandardAdapterDelegate())
            addDelegate(FeedStoryAdapterDelegate())

DjakaTechnology

class WithoutHolderActivity : AppCompatActivity() {
    private val adapter = GenericAdapter(Utils.getFeedItems())

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

        initAdapter()
        initRV()
    }