Not show Navigation button (hamburger button) - androidx

Question

Android Studio 3.4.
app/build.gradle:
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'androidx.appcompat:appcompat:1.1.0-alpha04'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation "android.arch.navigation:navigation-fragment-ktx:1.0.0-beta02"
implementation "android.arch.navigation:navigation-ui-ktx:1.0.0-beta02"
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.widget.Toolbar
import androidx.drawerlayout.widget.DrawerLayout
import androidx.navigation.NavController
import androidx.navigation.Navigation.findNavController
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.navigateUp
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController
import com.google.android.material.navigation.NavigationView
class MainActivity : AppCompatActivity() {
private lateinit var appBarConfiguration: AppBarConfiguration
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val toolbar = findViewById<Toolbar>(R.id.toolbar)
setSupportActionBar(toolbar)
val navController = findNavController(R.id.my_nav_host_fragment)
val drawerLayout: DrawerLayout? = findViewById(R.id.drawer_layout)
val navigationMenu = findViewById<NavigationView>(R.id.nav_view)!!.menu
appBarConfiguration = AppBarConfiguration(navigationMenu, drawerLayout)
setupActionBar(navController, appBarConfiguration)
setupNavigationMenu(navController)
}
private fun setupNavigationMenu(navController: NavController) {
val sideNavView = findViewById<NavigationView>(R.id.nav_view)
sideNavView?.setupWithNavController(navController)
}
private fun setupActionBar(navController: NavController, appBarConfig: AppBarConfiguration) {
setupActionBarWithNavController(navController, appBarConfig)
}
override fun onSupportNavigateUp(): Boolean {
return findNavController(R.id.my_nav_host_fragment).navigateUp(appBarConfiguration)
}
}
layout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout
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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/colorPrimary"
android:theme="#style/ThemeOverlay.AppCompat.Dark"/>
<fragment
android:id="#+id/my_nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
/>
</LinearLayout>
<com.google.android.material.navigation.NavigationView
android:id="#+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
app:menu="#menu/nav_drawer_menu"/>
</androidx.drawerlayout.widget.DrawerLayout>
here result:
why not show navigation button (hamburger) ?