Android Studio Spinner (in Kotlin) doesn't respond to any clicks - android-studio

Question

I am trying to get a spinner working with Kotlin, I have spent hours on it but to no avail. Whatever I do, it doesn't respond to items being selected.
Let's start with the code:
This is my xml layout: (only the spinner)
<Spinner
android:id="#+id/unitySelectionSpinner"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="50"
android:gravity="center"
android:textSize="24sp"
/>
My Fragment:
import android.app.Activity
import android.content.Context
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Spinner
import android.widget.Toast
import androidx.databinding.DataBindingUtil
import androidx.navigation.Navigation
import com.epfl.esl.organizer.databinding.FragmentCreateStorageBinding
import com.google.firebase.database.*
import kotlin.collections.ArrayList
class CreateStorageFragment : Fragment(), AdapterView.OnItemSelectedListener {
private lateinit var binding: FragmentCreateStorageBinding
private lateinit var unitID: String
val database: FirebaseDatabase = FirebaseDatabase.getInstance("myDatabase")
val storageRef: DatabaseReference = database.getReference("Units")
var list = ArrayList<String>()
override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
Toast.makeText(context, "We got the Key:", Toast.LENGTH_SHORT).show()
var a = 7 / 0
}
override fun onNothingSelected(parent: AdapterView<*>?) {
Toast.makeText(context, "Nothing selected", Toast.LENGTH_SHORT).show()
var b = 7 / 0
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_create_storage, container, false)
// Get the list of names of units from firebase
storageRef.addListenerForSingleValueEvent(object: ValueEventListener{
override fun onDataChange(snapshot: DataSnapshot) {
// Fill an ArrayList with all the unit names
for(unit in snapshot.children) {
list.add(unit.child("unitName").value.toString())
}
}
override fun onCancelled(error: DatabaseError) {}
})
binding.addObjectButton.setOnClickListener{view: View ->
Navigation.findNavController(view).navigate(R.id.action_createStorageFragment_to_createObjectFragment)
}
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val spinner: Spinner = binding.unitySelectionSpinner
val spinnerArrayAdapter = ArrayAdapter<String>(activity as Context, android.R.layout.simple_spinner_dropdown_item, list)
spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
spinner.adapter = spinnerArrayAdapter
spinner.onItemSelectedListener = this
}
}
I feel that I've tried everything imaginable, including:
-Creating an independent class with the spinner functions (onItemSelected, etc.)
-Put everything in onCreateView, put everything in onViewCreated
-Creating an instance of spinner with AdapterView.OnItemSelectedListener inside onCreateView
Whatever I do the result is always the same: the spinner is populated (all the firebase data is written into it properly) but it doesn't respond when I click on an item in the app. None of the toasts (or the crash that should be caused by the division by zero) are triggered. It simply closes on selection as a normal spinner would do.
I am not sure what I am missing here. Any ideas?