https://medium.com/codex/android-material-navigation-rail-d44eeb27d111 - Navigation Rail Early Look

BadgesCodeExample.kt

// If you don't add a number, only a badge will be displayed at the respective menu_item
var badge = findViewById<NavigationRailView>(R.id.navigation_rail).getOrCreateBadge(R.id.menu_item_account)
badge.isVisible = true

// In this case, the number 99 will be displayed in the badge
badge = findViewById<NavigationRailView>(R.id.navigation_rail).getOrCreateBadge(R.id.menu_item_moon)
badge.isVisible = true
badge.number = 99

build.gradle

  dependencies {
    // ...
    implementation 'com.google.android.material:material:1.4.0-alpha01'
    // ...
  }

MainActivity.kt

 NavigationRailView.OnNavigationItemSelectedListener { item ->
            when(item.itemId) {
                R.id.menu_item_account -> {
                    // Account item in NavigationRail clicked
                    true
                }
                R.id.menu_item_moon -> {
                    // Moon item in NavigationRail clicked
                    true
                }
                R.id.menu_item_time -> {
                    // Time item in NavigationRail clicked
                    true
                }
                else -> false
            }
        }

navigation-rail-example-layout-integration.xml

<com.google.android.material.navigationrail.NavigationRailView
    android:id="@+id/navigation_rail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:headerLayout="@layout/navigation_rail_header"
    app:menu="@menu/navigation_rail_menu" />

navigation_rail_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/menu_item_account"
        android:enabled="true"
        android:icon="@drawable/ic_account"
        android:title="@string/menu_item_account_label"/>
    <item
        android:id="@+id/menu_item_moon"
        android:enabled="true"
        android:icon="@drawable/ic_moon"
        android:title="@string/menu_item_moon_label"/>
    <item
        android:id="@+id/menu_item_time"
        android:enabled="true"
        android:icon="@drawable/ic_time"
        android:title="@string/menu_item_time_label"/>
</menu>