Saving a variable when exiting an application

Question

I am really new to Android Studio(I just started yesterday) and I'm coding a sort of clicker game(in XML and kotlin). I wanted the click counter (which is in a textview with a text at the begining) to save when leaving the app and loading when launching. I looked up savepreferences but I don't really understand how it works .. Could you guys help me please ?

`class MainActivity : AppCompatActivity() {

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

    val one:ImageButton = findViewById<ImageButton>(R.id.iv_image)
    val mp: MediaPlayer = MediaPlayer.create(this, R.raw.click)
    var mCounter = 0
    var txv = findViewById<TextView>(R.id.tx)
    one.setOnClickListener {
        //Play sound when click
        mp.start()
        //Increment click counter
        mCounter++
        txv.text = "Fixed mistakes:  " + mCounter.toString()
    }
}

}`

Any help is welcomed :)

EDIT: I posted some code that i did with savedpreferences but it is not fully functionnal. I would gladly appreciate some help ^^

EDIT V2: look at the comments for the solution

Answer 1

EDIT V2: I did it, here is the code `class MainActivity : AppCompatActivity() {

//Counter lateinit initialisation
var mCounter by Delegates.notNull<Int>()

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

    //Load la sauvegarde
    loadData()

    val one:ImageButton = findViewById<ImageButton>(R.id.iv_image)
    val mp: MediaPlayer = MediaPlayer.create(this, R.raw.click)
    var txv = findViewById<TextView>(R.id.tx)

    //ON CLICK
    one.setOnClickListener {
        //Play le son quand on clique
        mp.start()
        //Compteur de click
        mCounter++
        txv.text = "Fixed mistakes:  $mCounter"
        saveData()
    }
}

private fun saveData() {
    val sharedPreferences = getSharedPreferences("sharedPrefs" , 0)
    val editor = sharedPreferences.edit()
    editor.putInt("INT_KEY", mCounter)
    editor.commit()
}

private fun loadData() {
    val sharedPreferences = getSharedPreferences("sharedPrefs" , 0)
    mCounter = sharedPreferences.getInt("INT_KEY", 0)
}

}`