Android - Save ArrayList to SharedPreferences with Kotlin

package com.gtappdevelopers.kotlingfgproject

data class CourseRVModal(
    // on below line we are creating a two
    // variable one for course name 
    // and other for course image.
    var courseName: String,
    var courseImg: Int
)

package com.gtappdevelopers.kotlingfgproject

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView

// on below line we are creating
// a course rv adapter class.
class CourseRVAdapter(
    // on below line we are passing variables
    // as course list and context
    private var courseList: ArrayList<CourseRVModal>,
) : RecyclerView.Adapter<CourseRVAdapter.CourseViewHolder>() {
    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): CourseRVAdapter.CourseViewHolder {
        // this method is use to inflate the layout file 
        // which we have created for our recycler view.
        // on below line we are inflating our layout file.
        val itemView = LayoutInflater.from(parent.context).inflate(
            R.layout.course_rv_item,
            parent, false
        )
        // at last we are returning our view holder
        // class with our item View File.
        return CourseViewHolder(itemView)
    }
    
    override fun onBindViewHolder(holder: CourseRVAdapter.CourseViewHolder, position: Int) {
        // on below line we are setting data to our text view and our image view.
        holder.courseNameTV.text = courseList.get(position).courseName
        holder.courseIV.setImageResource(courseList.get(position).courseImg)
    }

    override fun getItemCount(): Int {
        // on below line we are returning 
        // our size of our list
        return courseList.size
    }

    class CourseViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        // on below line we are initializing our course name text view and our image view.
        val courseNameTV: TextView = itemView.findViewById(R.id.idTVCourse)
        val courseIV: ImageView = itemView.findViewById(R.id.idIVCourse)
    }
}

package com.gtappdevelopers.kotlingfgproject

import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.ImageView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.RecyclerView
import com.google.gson.Gson
import com.google.gson.reflect.TypeToken
import java.lang.reflect.Type

class MainActivity : AppCompatActivity() {

    // on below line we are creating 
    // a variable for our button
    lateinit var androidIV: ImageView
    lateinit var cIV: ImageView
    lateinit var javaIV: ImageView
    lateinit var jsIV: ImageView
    lateinit var pythonIV: ImageView
    lateinit var languageRV: RecyclerView
    lateinit var saveBtn: Button
    lateinit var lngEdt: EditText

    lateinit var courseList: ArrayList<CourseRVModal>
    lateinit var courseRVAdapter: CourseRVAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // on below line we are initializing 
        // our views with their ids.
        androidIV = findViewById(R.id.idIVAndroid)
        cIV = findViewById(R.id.idIVC)
        javaIV = findViewById(R.id.idIVJava)
        jsIV = findViewById(R.id.idIVJs)
        pythonIV = findViewById(R.id.idIVPython)
        languageRV = findViewById(R.id.idRVLanguages)
        saveBtn = findViewById(R.id.idBtnSaveList)
        lngEdt = findViewById(R.id.idEdtLanguage)

        // method to load arraylist from shared prefs
        // initializing our shared prefs with name as
        // shared preferences.
        val sharedPreferences = getSharedPreferences("shared preferences", MODE_PRIVATE)

        // creating a variable for gson.
        val gson = Gson()

        // below line is to get to string present from our
        // shared prefs if not present setting it as null.
        val json = sharedPreferences.getString("courses", null)

        // below line is to get the type of our array list.
        val type: Type = object : TypeToken<ArrayList<CourseRVModal?>?>() {}.type

        // in below line we are getting data from gson
        // and saving it to our array list
        courseList = gson.fromJson<Any>(json, type) as ArrayList<CourseRVModal>

        // checking below if the array list is empty or not
        if (courseList == null) {
            // if the array list is empty
            // creating a new array list.
            courseList = ArrayList()
        }

        // on below line we are initializing our adapter 
        // and setting it to recycler view.
        courseRVAdapter = CourseRVAdapter(courseList)
        languageRV.adapter = courseRVAdapter

        androidIV.setOnClickListener {
            if (lngEdt.text.toString().isNotEmpty()) {
                // on below line adding item to recycler view.
                addItemToList(lngEdt.text.toString(), R.drawable.android)
            }
        }

        cIV.setOnClickListener {
            if (lngEdt.text.toString().isNotEmpty()) {
                // on below line adding item to recycler view.
                addItemToList(lngEdt.text.toString(), R.drawable.c)
            }
        }

        javaIV.setOnClickListener {
            if (lngEdt.text.toString().isNotEmpty()) {
                // on below line adding item to recycler view.
                addItemToList(lngEdt.text.toString(), R.drawable.java)
            }
        }

        jsIV.setOnClickListener {
            if (lngEdt.text.toString().isNotEmpty()) {
                // on below line adding item to recycler view.
                addItemToList(lngEdt.text.toString(), R.drawable.js)
            }
        }

        pythonIV.setOnClickListener {
            if (lngEdt.text.toString().isNotEmpty()) {
                // on below line adding item to recycler view.
                addItemToList(lngEdt.text.toString(), R.drawable.python)
            }
        }

        // on below line we are adding 
        // click listener for our save button
        saveBtn.setOnClickListener {
 
            // method for saving the data in array list.
            // creating a variable for storing data in
            // shared preferences.
            val sharedPreferences = getSharedPreferences("shared preferences", MODE_PRIVATE)          

            // creating a variable for editor to
            // store data in shared preferences.
            val editor = sharedPreferences.edit()        

            // creating a new variable for gson.
            val gson = Gson()            

            // getting data from gson and storing it in a string.
            val json: String = gson.toJson(courseList)
           
            // below line is to save data in shared
            // prefs in the form of string.
            editor.putString("courses", json)

            // below line is to apply changes
            // and save data in shared prefs.
            editor.apply()

            // after saving data we are displaying a toast message.
            Toast.makeText(this, "Saved Array List to Shared preferences. ", Toast.LENGTH_SHORT)
                .show()

        }
    }

    private fun addItemToList(lngName: String, lngImg: Int) {
        // in this method we are adding item to list and 
        // notifying adapter that data has changed
        courseList.add(CourseRVModal(lngName, lngImg))
        courseRVAdapter.notifyDataSetChanged()
    }
}

import android.content.Context
import android.content.SharedPreferences

class MainActivity : AppCompatActivity() {
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // Create an ArrayList of strings
        val myArrayList = arrayListOf("item1", "item2", "item3")
        
        // Save the ArrayList to SharedPreferences
        saveArrayListToSharedPreferences("myArrayList", myArrayList)
        
        // Retrieve the saved ArrayList from SharedPreferences
        val retrievedArrayList = getArrayListFromSharedPreferences("myArrayList")
        
        // Print the retrieved ArrayList to the console
        Log.d("TAG", "Retrieved ArrayList: $retrievedArrayList")
    }
    
    private fun saveArrayListToSharedPreferences(key: String, arrayList: ArrayList<String>) {
        // Convert the ArrayList to a Set of strings
        val mySet = arrayList.toSet()
        
        // Get an instance of the SharedPreferences
        val sharedPreferences = getSharedPreferences("my_prefs", Context.MODE_PRIVATE)
        
        // Get an instance of the SharedPreferences.Editor
        val editor = sharedPreferences.edit()
        
        // Put the Set of strings into the SharedPreferences.Editor
        editor.putStringSet(key, mySet)
        
        // Apply the changes to the SharedPreferences
        editor.apply()
    }
    
    private fun getArrayListFromSharedPreferences(key: String): ArrayList<String> {
        // Get an instance of the SharedPreferences
        val sharedPreferences = getSharedPreferences("my_prefs", Context.MODE_PRIVATE)
        
        // Retrieve the Set of strings from SharedPreferences
        val mySet = sharedPreferences.getStringSet(key, emptySet())
        
        // Convert the Set of strings back to an ArrayList
        val myArrayList = arrayListOf<String>()
        myArrayList.addAll(mySet!!)
        
        return myArrayList
    }
}