How to permanently hide the Navigation Bar in an Android activity using Kotlin?

This example demonstrates how to permanently hide the Navigation Bar in an Android activity using Kotlin.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="70dp"
      android:background="#008080"
      android:padding="5dp"
      android:text="TutorialsPoint"
      android:textColor="#fff"
      android:textSize="24sp"
      android:textStyle="bold" />
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:text="Hello World!"
      android:textColor="@android:color/holo_blue_dark"
      android:textSize="24sp"
      android:textStyle="bold" />
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.kt
import android.os.Build
import android.os.Bundle
import android.view.View
import androidx.appcompat.app.AppCompatActivity
@Suppress("DEPRECATED_IDENTITY_EQUALS", "DEPRECATION")
class MainActivity : AppCompatActivity() {
   private var currentApiVersion: Int = 0
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      currentApiVersion = Build.VERSION.SDK_INT
      val flags: Int = View.SYSTEM_UI_FLAG_LAYOUT_STABLE or
      View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION or
      View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or
      View.SYSTEM_UI_FLAG_FULLSCREEN or View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
      if (currentApiVersion >= Build.VERSION_CODES.KITKAT) {
         window.decorView.systemUiVisibility = flags
         val decorView: View = window.decorView
         decorView.setOnSystemUiVisibilityChangeListener { visibility ->
         if (visibility and View.SYSTEM_UI_FLAG_FULLSCREEN === 0) {
            decorView.systemUiVisibility = flags
         }
      }
      }
   }
   override fun onWindowFocusChanged(hasFocus: Boolean) {
      super.onWindowFocusChanged(hasFocus)
      if (currentApiVersion >= Build.VERSION_CODES.KITKAT && hasFocus) {
         window.decorView.systemUiVisibility = View.SYSTEM_UI_FLAG_LAYOUT_STABLE or
         View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION or
         View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION or
         View.SYSTEM_UI_FLAG_FULLSCREEN or View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
      }
   }
}
Step 4 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.q11">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen