How to retrieve a field in firebase with user id - firebase

Question

I am implementing a quiz app in Android studio using kotlin. I am communicating with firebase where I store users who signs up. This is how it is structured in firebase:
And this is how I save a user when they signed up:
class User(val uid: String, val Username: String, var highscore: Int)
private fun saveUserToDatabase(){
val uid: String? = FirebaseAuth.getInstance().uid
val ref: DatabaseReference = FirebaseDatabase.getInstance().getReference( "/Users/$uid")
val user = User(uid.toString(), signUpUsername.text.toString(), 0)
ref.setValue(user)
.addOnSuccessListener {
Log.d("RegisterActivity", "User was saved in the database")
}
}
}
When a user has logged in and have played a round I want to retrieve the highscore with the current users userId and update the highscore if the score is greater than the highscore. This is my function that handles that:
private fun updateScore(score: Int, userId: String, isLoggedIn: Boolean){
if(isLoggedIn) {
var ref = FirebaseDatabase.getInstance().reference
ref.child(userId).addListenerForSingleValueEvent(object : ValueEventListener {
override fun onCancelled(error: DatabaseError) {
Log.e("onCancelledError", "onCancelled", error.toException())
}
override fun onDataChange(dataSnapShot: DataSnapshot) {
var highscore = dataSnapShot.child("highscore").getValue(Int::class.java)
Log.d("highscore", highscore.toString())
if(highscore != null){
if (highscore < score) {
highscore = score
dataSnapShot.ref.setValue(highscore)
}
}
}
})
}
}
But this does not work because highscore is null, when it should be 0. My userId is right so it is not that, I do not know what is wrong. Since I am new to firebase I have a hard time understanding the syntax. Any suggestions what could be wrong?
Thanks!

Answer 1

You're not building the reference to the user's node correctly. You probably meant to do this:
ref.child('Users').child(userId).addListenerForSingleValueEvent(...)
Note child('Users').