Recycler View Android Kotlin

Recycler View Tutorial

Create a Android Studio Project :

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {
    private lateinit var editItem:EditText
    private lateinit var btnAdd:Button
    private lateinit var recyclerView: RecyclerView

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

     
    }

    private fun fetchData():ArrayList<String>{
        val list = ArrayList<String>()
        for(i in 0 until 100){
            list.add("Item No : $i")
        }
        return list
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/edit_item"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginTop="36dp"
        android:layout_marginEnd="24dp"
        android:layout_marginBottom="16dp"
        android:ems="10"
        android:hint="Enter Todo..."
        android:inputType="textPersonName"
        app:layout_constraintBottom_toTopOf="@+id/text_view"
        app:layout_constraintEnd_toStartOf="@+id/btn_add"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" />

    <Button
        android:id="@+id/btn_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="24dp"
        android:text="Add"
        app:layout_constraintBottom_toBottomOf="@+id/edit_item"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toEndOf="@+id/edit_item"
        app:layout_constraintTop_toTopOf="@+id/edit_item"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:layout_marginBottom="36dp"
        android:fontFamily="sans-serif-medium"
        android:text="Your List"
        android:textColor="@android:color/background_dark"
        android:textSize="18sp"
        app:layout_constraintBottom_toTopOf="@+id/recycler_view"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/edit_item" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginTop="28dp"
        android:layout_marginBottom="16dp"
        android:paddingHorizontal="24dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/text_view" />
</androidx.constraintlayout.widget.ConstraintLayout

2. Now Our Basic App is Ready. Create a new Kotlin class ListItemAdapter which extends RecyclerView Adapter.

ListItemAdapter.kt

import android.view.LayoutInflater
import androidx.recyclerview.widget.RecyclerView
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.content.res.ColorStateListInflaterCompat.inflate

class ItemListAdapter(val items:ArrayList<String>) : RecyclerView.Adapter<ItemViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.item_recycler,parent,false);
        return ItemViewHolder(view)
    }

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

    override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
        val currentItem = items[position]
        holder.titleView.text = currentItem
    }

}

class ItemViewHolder(itemView:View): RecyclerView.ViewHolder(itemView) {
    val titleView: TextView = itemView.findViewById(R.id.txt_item_name);

}

3.Now Create a new layout which the recycler view will display.

Create item_list.xml

item_list.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <TextView
        android:id="@+id/txt_item_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="16sp"
        android:paddingHorizontal="20dp"
        android:paddingVertical="10dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>