Kotlin ListView IndexOutOfBoundsException - kotlin

Question

(new to kotlin) I'm making my own music app but i'm having an error that i don't understand :
in the bit of code where i try to access a random view (shuffle), i get the java.lang.IndexOutOfBoundsException: Index:96 Size:11.
96 in this example is the view in the listview that i'm trying to access.
It happens in this line : var iView = listViewMusic.get(idShuffle)
Same if i use listViewMusic[idShuffle]
EDIT : Turns out that 11 is only the 11 visible items on screen at any given moment, even if the list contains hundreds of items. When i use listViewMusic.smoothscrolltoposition(idShuffle) it works, but the size of 11 now relates to the 11 on screen after the scrolling
The function playNext() inside the activity, called when clicking on the shuffle button:
fun playNext(){
try {
// Find the order of the next song to play
var idShuffle = musicAdapter!!.getIdofItem(listMusicShuffled.get(musicNextToPlay).title)
// Find the right record in the list
//var iView = listViewMusic[idShuffle]
//toastIt(applicationContext, "adapter count ${listViewMusic.adapter.count}")
//toastIt(applicationContext, "listview count ${listViewMusic.count}")
var iView = listViewMusic.get(idShuffle) //throws the error
// Play it
playOrPause(iView)
// Prepare the next track
musicNextToPlay += 1
if (musicNextToPlay >= listMusicShuffled.size) {
musicNextToPlay = -1
}
} catch (e:Exception) {toastException(applicationContext, "playnext", e) }
}
The part of the function onCreate that fills in the listViewMusic:
// Retrieve the data
val mediaStoreUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI
val cursor = contentResolver.query(mediaStoreUri, null, "", null, null)
//Browse the data
listMusic = mutableListOf()
val listMusicJson = getMusicFromJson()
while (cursor!!.moveToNext()) {
val musicName = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME))
val musicArtist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST))
val musicUrl = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA))
val musicType:String =
if (musicArtist.contains("lmdmf", true)) { "LMDMF" }
else if (musicName.contains("slack", true)) { "SLACK" }
else { "MUSIC" }
listMusic.add(
MusicTrack(
musicName,
musicPlayCount,
musicUrl,
musicType
)
)
}
cursor.close()
musicAdapter = MusicAdapter(listMusic.sortedWith(compareBy<MusicTrack>{ it.title }).filter { it.type == "MUSIC"}.toMutableList())
listViewMusic.adapter = musicAdapter