How to use Recyclerview Adapter in Android Kotlin

In RecyclerView, there are several built-in functions that you can use to manage and interact with the items in the list. Here is an overview of some of the most commonly used functions:

RecyclerView Adapter Functions

1. onCreateViewHolder

   • This function is called when a new ViewHolder is created. You inflate the item layout here.

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

2. onBindViewHolder

   • This function is called to display the data at the specified position.

   
   override fun onBindViewHolder(holder: NoteViewHolder, position: Int) {
       val note = notesList[position]
       holder.titleTextView.text = note.title
       holder.descriptionTextView.text = note.description
       holder.dateTextView.text = note.date
   }
   

3. getItemCount

   • This function returns the total number of items in the data set held by the adapter.

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

4. getItemId

   • This function returns the stable ID for the item at the given position. You need to override hasStableIds to return true.

   
   override fun getItemId(position: Int): Long {
       return notesList[position].id
   }
   
   override fun hasStableIds(): Boolean {
       return true
   }
   

RecyclerView ViewHolder Functions

1. getAdapterPosition

   • This function returns the position of the ViewHolder in the adapter.

   
   val position = holder.adapterPosition
   

2. getItemViewType

   • This function returns the view type of the item at the specified position.

   
   override fun getItemViewType(position: Int): Int {
       return super.getItemViewType(position)
   }
   

3. setIsRecyclable

   • This function sets whether this ViewHolder can be recycled.

   
   holder.setIsRecyclable(false)
   

RecyclerView LayoutManager Functions

1. findViewByPosition

   • This function finds the view corresponding to the given adapter position.

   
   val view = layoutManager.findViewByPosition(position)
   

2. scrollToPosition

   • This function scrolls the RecyclerView to the specified adapter position.

   
   recyclerView.scrollToPosition(position)
   

3. smoothScrollToPosition

   • This function smoothly scrolls the RecyclerView to the specified adapter position.

   
   recyclerView.smoothScrollToPosition(position)
   

4. getChildAt

   • This function returns the child view at the specified index.

   
   val childView = recyclerView.getChildAt(index)
   

5. getPosition

   • This function returns the adapter position of the specified child view.

   
   val position = recyclerView.getChildAdapterPosition(childView)
   

Example: Extended RecyclerView Adapter with More Functions

Here's an extended example of a RecyclerView Adapter with more functionalities, including item ID management:

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView

class NotesAdapter(private val notesList: List<Note>) : RecyclerView.Adapter<NotesAdapter.NoteViewHolder>() {

    init {
        setHasStableIds(true)
    }

    class NoteViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val titleTextView: TextView = itemView.findViewById(R.id.titleTextView)
        val descriptionTextView: TextView = itemView.findViewById(R.id.descriptionTextView)
        val dateTextView: TextView = itemView.findViewById(R.id.dateTextView)
    }

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

    override fun onBindViewHolder(holder: NoteViewHolder, position: Int) {
        val note = notesList[position]
        holder.titleTextView.text = note.title
        holder.descriptionTextView.text = note.description
        holder.dateTextView.text = note.date

        // Example of getting adapter position and setting a click listener
        holder.itemView.setOnClickListener {
            val pos = holder.adapterPosition
            // Handle the click event
        }
    }

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

    override fun getItemId(position: Int): Long {
        return notesList[position].id
    }

    override fun getItemViewType(position: Int): Int {
        return super.getItemViewType(position)
    }
}

This example includes item click handling and stable ID management. You can add more functionalities and customize them according to your requirements.