Add SearchView to Custom Toolbar in a Fragment

Question

I am trying to add a SearchView to my custom Toolbar. I've tried adding the SearchView directly to the Toolbar with toolbar.addView(searchView) but it didn't change anything, I am getting a blank Toolbar no matter what I try. What am I doing wrong? this should be simple...

Toolbar:

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.Light"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light">

</androidx.appcompat.widget.Toolbar>

Search Menu:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_search"
        android:icon="@drawable/ic_search"
        android:title="Search"
        app:actionViewClass="androidx.appcompat.widget.SearchView"
        app:showAsAction="ifRoom|collapseActionView" />

</menu>

Fragment:

lateinit var toolbar: Toolbar

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    view = ConstraintLayout(this.context)
    view.layoutParams = ConstraintLayout.LayoutParams(ConstraintLayout.LayoutParams.MATCH_PARENT, ConstraintLayout.LayoutParams.MATCH_PARENT)
    toolbar = inflater.inflate(R.layout.toolbar, container, false) as Toolbar
    setHasOptionsMenu(true)
    return view
}


override fun onCreateOptionsMenu(menu: Menu?, inflater: MenuInflater?) {
    super.onCreateOptionsMenu(menu, inflater)

    // Inflate the options menu from XML
    inflater?.inflate(R.menu.search_menu, menu)

    val searchItem = menu?.findItem(R.id.action_search)
    val searchView = searchItem?.actionView as SearchView

    searchView.imeOptions = EditorInfo.IME_ACTION_DONE
    searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
        override fun onQueryTextSubmit(p0: String?): Boolean {
            return false
        }

        override fun onQueryTextChange(p0: String?): Boolean {
            //adapter.getFilter().filter(newText);
            return false
        }
    })

    toolbar.addView(searchView)
}

Answer 1

Solved it with adding setSupportActionBar(toolbar) in onCreateView()