Firebase database not loading images in image slider

Question

I have made this program to retrieve images from firebase database in image slider but it is showing error in addListenerForSingleValueEvent and when checking error it generate some kind of private function but then also after running the app it is not showing anything it is coming blank.

class HomeActivity : AppCompatActivity() {

    lateinit var imageSlider: ImageSlider
    lateinit var ref: DatabaseReference

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_home)
      
        ref = FirebaseDatabase.getInstance().getReference().child("Slider")

        imageSlider = findViewById<ImageSlider>(R.id.imageslider)
        val remoteimages: List<SlideModel> = ArrayList()

           ref.addListenerForSingleValueEvent(object : ValueEventListener {
                override fun onDataChange(snapshot: DataSnapshot) {
                    for (h in snapshot.children)
                        remoteimages.add(SlideModel(
                                h.child("url").getValue().toString(),
                                h.child("title").getValue().toString(),
                                ScaleTypes.FIT))

                    imageSlider.setImageList(remoteimages, ScaleTypes.FIT)
                }

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