As I see in your database, the key of all User objects that are stored within Users node, are not added using the UID that comes from the authentication process, those key as generated with the push() method, because all of them start with -.

The most appropriate solution might be to change those keys and get then the data accordingly. To add a User object, you should some lines of code that looks like this:

val uid = FirebaseAuth.getInstance().currentUser!!.uid
val rootRef = FirebaseDatabase.getInstance().reference
val usersRef = rootRef.child("Users")
usersRef.child(uid).setValue(user)

To display the name of the logged-in users, simply use the following lines of code:

val valueEventListener = object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        val name = dataSnapshot.child("name").getValue(String::class.java)
        Log.d("TAG", name)

        //Do what you need to do with the value of name
    }

    override fun onCancelled(databaseError: DatabaseError) {
        Log.d("TAG", databaseError.getMessage()) //Don't ignore errors!
    }
}
usersRef.child(uid).addListenerForSingleValueEvent(valueEventListener)

Try this code instead :

 val reference = FirebaseDatabase.getInstance().getReference("Users").child(auth?.currentUser?.uid)
    reference.addValueEventListener(object : ValueEventListener {
        override fun onDataChange(dataSnapshot: DataSnapshot) {
           for(snapshot in dataSnapShot.children){
          val username = 
               snapshot.child("username").value.toString()
            if (username == null)
                fragmentView?.name?.setText("Hello, Anonymous")
            else
                fragmentView?.name?.setText("Hello, $username")
        }        
                     }
          

        override fun onCancelled(databaseError: DatabaseError) {}
    })

I am trying to display the current username from the Realtime Database but whenever I am running my code it gives me null. Here is my code:

    val reference =FirebaseDatabase.getInstance().reference
    currentUserUid = auth?.currentUser?.uid
    reference.addValueEventListener(object : ValueEventListener {
        override fun onDataChange(dataSnapshot: DataSnapshot) {
            val username =
                dataSnapshot.child(auth!!.currentUser!!.uid).child("Users")
                    .child("username")
                    .getValue(String::class.java)
            if (username == null)
                fragmentView?.name?.setText("Hello, Anonymous")
            else
                fragmentView?.name?.setText("Hello, $username")
        }

        override fun onCancelled(databaseError: DatabaseError) {}
    })

This is my content to code

package com.example.videoapp.Model

data class ContentDTO(var explain : String? = null,
                      var imageUrl : String? = null,
                      var uid : String? = null,
                      var userId : String? = null,
                      var username : String? = null,
                      var timestamp : Long? = null,
                      var favoriteCount : Int = 0,
                      var favorites : MutableMap<String,Boolean> = HashMap()){
    data class Comment(var uid : String? = null,
                       var userId : String? = null,
                       var comment : String? = null,
                       var timestamp : Long? = null)
}

This is my code where I can upload the pics. I have taken a little bit of help from the internet to do that. I am trying to display the name here but it’s returning nothing

val storageRef = storage?.reference?.child("images")?.child(imageFileName)
storageRef?.putFile(photoUri!!)?.continueWithTask { task: com.google.android.gms.tasks.Task<com.google.firebase.storage.UploadTask.TaskSnapshot> ->
    [email protected] storageRef.downloadUrl
}?.addOnSuccessListener { uri ->
    val contentDTO = com.example.videoapp.Model.ContentDTO()

    //Insert downloadUrl of image
    contentDTO.imageUrl = uri.toString()

    //Insert uid of user
    contentDTO.uid = auth?.currentUser?.uid

    //Insert userId
    contentDTO.userId = auth?.currentUser?.email
    contentDTO.username = auth?.currentUser?.displayName

    //Insert explain of content
    contentDTO.explain = addphoto_edit_explain2.text.toString()

    //Insert timestamp
    contentDTO.timestamp = System.currentTimeMillis()

    firestore?.collection("images")?.document()?.set(contentDTO)

    setResult(android.app.Activity.RESULT_OK)

    finish()
}