Speech to Text Application in Android with Kotlin

package com.gtappdevelopers.kotlingfgproject

import android.content.Intent
import android.os.Bundle
import android.speech.RecognizerIntent
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.util.*

class MainActivity : AppCompatActivity() {
  
    // on below line we are creating variables
    // for text view and image view
    lateinit var outputTV: TextView
    lateinit var micIV: ImageView

    // on below line we are creating a constant value
    private val REQUEST_CODE_SPEECH_INPUT = 1

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // initializing variables of list view with their ids.
        outputTV = findViewById(R.id.idTVOutput)
        micIV = findViewById(R.id.idIVMic)
        
        // on below line we are adding on click
        // listener for mic image view.
        micIV.setOnClickListener {
            // on below line we are calling speech recognizer intent.
            val intent = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH)
            
            // on below line we are passing language model
            // and model free form in our intent
            intent.putExtra(
                RecognizerIntent.EXTRA_LANGUAGE_MODEL,
                RecognizerIntent.LANGUAGE_MODEL_FREE_FORM
            )
            
            // on below line we are passing our 
            // language as a default language.
            intent.putExtra(
                RecognizerIntent.EXTRA_LANGUAGE,
                Locale.getDefault()
            )
            
            // on below line we are specifying a prompt 
            // message as speak to text on below line.
            intent.putExtra(RecognizerIntent.EXTRA_PROMPT, "Speak to text")

            // on below line we are specifying a try catch block.
            // in this block we are calling a start activity
            // for result method and passing our result code.
            try {
                startActivityForResult(intent, REQUEST_CODE_SPEECH_INPUT)
            } catch (e: Exception) {
                // on below line we are displaying error message in toast
                Toast
                    .makeText(
                        this@MainActivity, " " + e.message,
                        Toast.LENGTH_SHORT
                    )
                    .show()
            }
        }
    }

    // on below line we are calling on activity result method.
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        
        // in this method we are checking request
        // code with our result code.
        if (requestCode == REQUEST_CODE_SPEECH_INPUT) {
            // on below line we are checking if result code is ok
            if (resultCode == RESULT_OK && data != null) {
              
                // in that case we are extracting the 
                // data from our array list
                val res: ArrayList<String> =
                    data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS) as ArrayList<String>
               
                // on below line we are setting data
                // to our output text view.
                outputTV.setText(
                    Objects.requireNonNull(res)[0]
                )
            }
        }
    }
}