android kotlin - Toolbar menu example

MainActivity.kt

package com.example.jetpack

import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

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

        // set toolbar as support action bar
        setSupportActionBar(toolbar).apply {
            title = "Toolbar Menu Example"
        }
    }

    // show the menu on toolbar
    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        val inflater = menuInflater
        inflater.inflate(R.menu.toolbar_menu,menu)
        return super.onCreateOptionsMenu(menu)
    }

    // toolbar menu item click listener
    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when(item.itemId){
            R.id.download->{
                textView.text = "Download clicked."
                return true
            }R.id.upload->{
                textView.text = "Upload clicked."
                return true
            }R.id.cancel->{
                textView.text = "Cancel clicked."
                return true
            }R.id.settings->{
                textView.text = "Settings clicked."
                return true
            }
        }
        return super.onOptionsItemSelected(item)
    }
}

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:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#CFCBBF"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="?attr/actionBarTheme"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:elevation="4dp"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        tools:text="TextView"
        style="@style/TextAppearance.MaterialComponents.Headline5"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar" />

</androidx.constraintlayout.widget.ConstraintLayout>

res/values/styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.MaterialComponents.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

</resources>

res/menu/toolbar_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/download"
        android:title="Download"
        android:icon="@drawable/ic_arrow_download"
        app:showAsAction="always" />
    <item
        android:id="@+id/upload"
        android:title="Upload"
        android:icon="@drawable/ic_cloud_upload"
        app:showAsAction="always" />
    <item
        android:id="@+id/cancel"
        android:title="Cancel"
        android:icon="@drawable/ic_cancel"
        app:showAsAction="ifRoom" />
    <item
        android:id="@+id/settings"
        android:title="Settings"
        android:icon="@drawable/ic_settings"
        app:showAsAction="never" />
</menu>