Android GridView in Kotlin

package com.gtappdevelopers.kotlingfgproject

// on below line we are creating a modal class.
data class GridViewModal(
    // we are creating a modal class with 2 member
    // one is course name as string and 
    // other course img as int.
    val courseName: String,
    val courseImg: Int
)

package com.gtappdevelopers.kotlingfgproject

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.BaseAdapter
import android.widget.ImageView
import android.widget.TextView

// on below line we are creating an 
// adapter class for our grid view.
internal class GridRVAdapter(
    // on below line we are creating two 
    // variables for course list and context
    private val courseList: List<GridViewModal>,
    private val context: Context
) :
    BaseAdapter() {
    // in base adapter class we are creating variables 
    // for layout inflater, course image view and course text view.
    private var layoutInflater: LayoutInflater? = null
    private lateinit var courseTV: TextView
    private lateinit var courseIV: ImageView

    // below method is use to return the count of course list
    override fun getCount(): Int {
        return courseList.size
    }

    // below function is use to return the item of grid view.
    override fun getItem(position: Int): Any? {
        return null
    }
    
    // below function is use to return item id of grid view.
    override fun getItemId(position: Int): Long {
        return 0
    }

    // in below function we are getting individual item of grid view.
    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View? {
        var convertView = convertView
        // on blow line we are checking if layout inflater 
        // is null, if it is null we are initializing it.
        if (layoutInflater == null) {
            layoutInflater =
                context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        }
        // on the below line we are checking if convert view is null. 
        // If it is null we are initializing it.
        if (convertView == null) {
            // on below line we are passing the layout file
            // which we have to inflate for each item of grid view.
            convertView = layoutInflater!!.inflate(R.layout.gridview_item, null)
        }
        // on below line we are initializing our course image view 
        // and course text view with their ids.
        courseIV = convertView!!.findViewById(R.id.idIVCourse)
        courseTV = convertView!!.findViewById(R.id.idTVCourse)
        // on below line we are setting image for our course image view.
        courseIV.setImageResource(courseList.get(position).courseImg)
        // on below line we are setting text in our course text view.
        courseTV.setText(courseList.get(position).courseName)
        // at last we are returning our convert view.
        return convertView
    }
}

package com.gtappdevelopers.kotlingfgproject

import android.os.Bundle
import android.widget.AdapterView
import android.widget.GridView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.util.*
import kotlin.collections.ArrayList

class MainActivity : AppCompatActivity() {

    // on below line we are creating 
    // variables for grid view and course list
    lateinit var courseGRV: GridView
    lateinit var courseList: List<GridViewModal>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
       
        // initializing variables of grid view with their ids.
        courseGRV = findViewById(R.id.idGRV)
        courseList = ArrayList<GridViewModal>()
       
        // on below line we are adding data to 
        // our course list with image and course name.
        courseList = courseList + GridViewModal("C++", R.drawable.c)
        courseList = courseList + GridViewModal("Java", R.drawable.java)
        courseList = courseList + GridViewModal("Android", R.drawable.android)
        courseList = courseList + GridViewModal("Python", R.drawable.python)
        courseList = courseList + GridViewModal("Javascript", R.drawable.js)

        // on below line we are initializing our course adapter
        // and passing course list and context.
        val courseAdapter = GridRVAdapter(courseList = courseList, this@MainActivity)
       
        // on below line we are setting adapter to our grid view.
        courseGRV.adapter = courseAdapter
        
        // on below line we are adding on item
        // click listener for our grid view.
        courseGRV.onItemClickListener = AdapterView.OnItemClickListener { _, _, position, _ ->
        
            // inside on click method we are simply displaying 
            // a toast message with course name.
            Toast.makeText(
                applicationContext, courseList[position].courseName + " selected",
                Toast.LENGTH_SHORT
            ).show()
        }

    }
}