Option Menu Using Kotlin in Android

1. Creating New Project in Kotlin

• Open Android Studio.
• Go to File => New => New Project.Give Name To your application. Then, check Include Kotlin Support and click next button.
• Select minimum SDK you need. However, we have selected 21 as minimum SDK. Then, click next button.
• Then, select Empty Activity => click next => click finish.

2.Here we have one XML file activity_main.xml

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:id="@+id/relative"
    tools:context="com.dharmendra.optionmenu.MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:textSize="20sp"
        android:textStyle="bold"
        android:textColor="@android:color/black"
        android:text="Click On 3 Dots on Action Bar " />

</RelativeLayout>

3.We need to create one more xml file inside res->menu folder.

First we have to Create folder name menu inside res folder. And inside menu folder we have to create xml file name option_menu.xml

option_menu Contain 5 Items first Two are to change Text Color and other 3 for change Background Color.

option_menu.xml

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


    <item
        android:id="@+id/magenta"
        android:title="Magenta" />
    <item
        android:id="@+id/yellow"
        android:title="Yellow" />


    <item
        android:id="@+id/red"
        android:title="Red" />
    <item
        android:id="@+id/blue"
        android:title="Blue" />
    <item
        android:id="@+id/green"
        android:title="green" />


</menu>

Right Click on menu folder. New->menu resource file provide name to file and click Ok.

option_menu.xml file contain options which we want to provide.

4.MainActivity.kt

package com.dharmendra.optionmenu

import android.graphics.Color
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.widget.RelativeLayout
import android.widget.TextView


 class MainActivity : AppCompatActivity() {

    //Define Objecct Of RelativeLayout
     lateinit var backgroud:RelativeLayout

   // 
Define Objecct Of TextView

     lateinit var textView:TextView

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

        //Find View By Id For TextView because We change the Color of text
        textView=findViewById<TextView>(R.id.textView) as TextView

        //Find View By Id For Main Layout because we chnage the Color of Backgroud
        backgroud=findViewById<RelativeLayout>(R.id.relative) as RelativeLayout
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {

        //Inflate menu
        menuInflater.inflate(R.menu.option_menu,menu)
        return true
    }

    //Method to Handle Option Item Click

    override fun onOptionsItemSelected(item: MenuItem?): Boolean {

        val selectedItem= item!!.itemId

        when(selectedItem){

            R.id.magenta->{
                //Change Text Color
                textView.setTextColor(Color.MAGENTA)
            }

            R.id.yellow->{
                //Change Text Color
                textView.setTextColor(Color.YELLOW)
            }

            R.id.red->{
                //Change Background Color
               backgroud.setBackgroundColor(Color.RED)
            }
            R.id.green->{
                //Change Background Color
                backgroud.setBackgroundColor(Color.GREEN)
            }
            R.id.blue->{
                //Change Background Color
                backgroud.setBackgroundColor(Color.BLUE)
            }
        }


        return super.onOptionsItemSelected(item)
    }
}

Output: