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">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rvTodoItems"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@+id/btnAddTodo"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/etTodoTitle"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="Enter Todo Title"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/btnAddTodo"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/btnAddTodo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add Todo"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/btnDeleteDoneTodo" />

    <Button
        android:id="@+id/btnDeleteDoneTodo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Delete Done"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />


</androidx.constraintlayout.widget.ConstraintLayout>

build.gradle

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.example.todolist"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.1'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'

    implementation 'com.google.android.material:material:1.3.0-alpha02'
}

item_todo.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"
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:paddingStart="8dp"
    android:paddingEnd="8dp">

    <TextView
        android:id="@+id/tvTodoTitle"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="Example"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/cbDone"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <CheckBox
        android:id="@+id/cbDone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

package com.example.todolist

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private lateinit var todoAdapter : TodoAdapter

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

        rvTodoItems.adapter = todoAdapter
        rvTodoItems.layoutManager = LinearLayoutManager(this)

        btnAddTodo.setOnClickListener {
            val todoTitle = etTodoTitle.text.toString()
            if(todoTitle.isNotEmpty()) {
                val todo = Todo(todoTitle)
                todoAdapter.addTodo(todo)
                etTodoTitle.text.clear()
            }
        }
        btnDeleteDoneTodo.setOnClickListener {
            todoAdapter.deleteDoneTodos()
        }
    }
}

Todo.kt

package com.example.todolist

data class Todo (
    val title:      String,
    var isChecked:  Boolean = false
)

TodoAdapter.kt

package com.example.todolist

import android.graphics.Paint.STRIKE_THRU_TEXT_FLAG
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.activity_main.view.*
import kotlinx.android.synthetic.main.item_todo.view.*

class TodoAdapter(
    private val todos: MutableList<Todo>
) : RecyclerView.Adapter<TodoAdapter.TodoViewHolder>() {

    class TodoViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TodoViewHolder {
        return TodoViewHolder(
            LayoutInflater.from(parent.context).inflate(
                R.layout.item_todo,
                parent,
                false
            )
        )
    }

    private fun toggleStrikeThrough(tvTodoTitle: TextView, isChecked: Boolean) {
        if(isChecked) {
            tvTodoTitle.paintFlags = tvTodoTitle.paintFlags or STRIKE_THRU_TEXT_FLAG
        } else {
            tvTodoTitle.paintFlags = tvTodoTitle.paintFlags and STRIKE_THRU_TEXT_FLAG.inv()
        }
    }

    fun addTodo(todo: Todo) {
        todos.add(todo)
        notifyItemInserted(todos.size -1)
    }

    fun deleteDoneTodos() {
        todos.removeAll { todo ->
            todo.isChecked
        }
        notifyDataSetChanged()
    }

    override fun onBindViewHolder(holder: TodoViewHolder, position: Int) {
        val curTodo = todos[position]
        holder.itemView.apply {
            tvTodoTitle.text = curTodo.title
            cbDone.isChecked = curTodo.isChecked
            toggleStrikeThrough(tvTodoTitle, curTodo.isChecked)
            cbDone.setOnCheckedChangeListener { _, isChecked ->
                toggleStrikeThrough(tvTodoTitle, isChecked)
                curTodo.isChecked = !curTodo.isChecked
            }
        }
    }

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

Waww

sc lama gan