AndroidX Toolbar type mismatch despite imports not present

Question

Why is Android Studio preventing me from setting an AndroidX Toolbar (within a CollapsingToolbarLayout) as the ActionBar? The list of imports doesn't even show what type of Toolbar I've imported so what am I supposed to do in this case?

Type mismatch: inferred type is androidx.appcompat.widget.Toolbar! but android.widget.Toolbar! was expected

XML

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/myCoordinatorLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/myAppBarLayout">

        <com.google.android.material.appbar.CollapsingToolbarLayout
                android:id="@+id/myCollapsingToolbarLayout"
                android:layout_width="match_parent"
                android:layout_height="250dp"
                android:fitsSystemWindows="true"
                app:layout_scrollFlags="scroll|snap|exitUntilCollapsed">

            <androidx.appcompat.widget.Toolbar
                    android:id="@+id/myToolbar"
                    android:layout_width="match_parent"
                    android:layout_height="?attr/actionBarSize"
                    app:layout_collapseMode="pin" />
        </com.google.android.material.appbar.CollapsingToolbarLayout>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/myRecyclerView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:scrollbars="vertical"
            android:scrollbarStyle="outsideInset"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Kotlin

import android.app.AlertDialog
import android.content.Intent
import android.graphics.Color
import android.net.Uri
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.view.View
import android.widget.LinearLayout
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.my_layout.*

class MainActivity : Activity() {
    private lateinit var arrayMainItems: Array<String>
    private lateinit var adapterGL: RVAdapterGL
    private lateinit var adapterLL: RVAdapterLL

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.my_layout)
    }

    override fun onStart() {
        super.onStart()

        setContentView(R.layout.my_layout)

        val mCoordinatorLayout = myCoordinatorLayout
        val mAppBarLayout = myAppBarLayout
        val mCollapsingToolbarLayout = myCollapsingToolbarLayout
        val mToolbar = myToolbar

        setActionBar(mToolbar)
        mToolbar.title = getString(R.string.app_name)
    }
}

Answer 1

When you do

seActionBar(...

You are using a method that expects

android.widget.Toolbar

But in the xml you are using the material toolbar

You can use

setSupportActionBar