Sample of showing OptionMenu

MainActivity.kt

package com.example.ashia.filereadtest

import android.content.Context
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuInflater
import android.view.MenuItem
import android.view.View
import android.widget.AdapterView
import android.widget.ListView
import android.widget.SimpleAdapter
import android.widget.Toast
import java.util.*



data class TestData(val name: String, val price: Int, val desc: String){

}

public class MainActivity : AppCompatActivity() {

    private fun makeData(name: String, price: Int, desc: String): Map<String, Any>{
        var res = HashMap<String, Any>();
        res.put("name", name);
        res.put("price", price.toString() + "(" + (price*1.08).toString() +")");
        res.put("data", TestData(name, price, desc));
        return res;




    }

    protected class ListItemClickListener(val context: Context): AdapterView.OnItemClickListener{
        override fun onItemClick(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
            if (parent == null){
                Toast.makeText(context,"no", Toast.LENGTH_LONG).show();
            }else {
                val item = parent.getItemAtPosition(position) as Map<String, Any>;
                val data = item["data"] as TestData;
                Toast.makeText(context, data.desc, Toast.LENGTH_LONG).show();
            }
        }

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


        val lvMenu = findViewById<ListView>(R.id.lvMenu);
        val menuList = mutableListOf<Map<String, Any>>();

        menuList.add(makeData("Agedofu", 100, "Fried tofu"));
        menuList.add(makeData("Inari", 200, "Sushi of fried tofu"));
        menuList.add(makeData("Kinudofu",  150, "Smooth tofu"));

        val from = arrayOf("name", "price");
        val to = intArrayOf(android.R.id.text1, android.R.id.text2);

        val adapter = SimpleAdapter(this, menuList, android.R.layout.simple_list_item_2, from, to);
        lvMenu.adapter = adapter;
        lvMenu.setOnItemClickListener(ListItemClickListener(this.applicationContext));



    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.menu, menu);
        return super.onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem?): Boolean {
        when(item?.itemId){
            R.id.menuListOptionHello -> {
                Toast.makeText(this, "Hello!", Toast.LENGTH_LONG).show();
            }
        }
        return super.onOptionsItemSelected(item)
    }
}

menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/menuListOptionHello"
        android:title="Item" />
</menu>