ProjectLaogai/app/src/main/res/menu/activity_main_drawer.xml

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

    <group android:checkableBehavior="single">
        <item android:id="@+id/nav_home" android:title="@string/home" android:icon="@drawable/ic_baseline_home_24dp"/>
        <item
                android:id="@+id/nav_mensa"
                android:icon="@drawable/ic_free_breakfast_black_24dp"
                android:title="@string/mensa"/>
        <item
                android:id="@+id/nav_timetable"
                android:icon="@drawable/ic_baseline_calendar_today_24dp"
                android:title="@string/timetable"/>
        <item
                android:id="@+id/nav_moodle"
                android:icon="@drawable/ic_menu_slideshow"
                android:title="@string/moodle"/>
        <item
                android:id="@+id/nav_email"
                android:icon="@android:drawable/ic_dialog_email"
                android:title="@string/e_mail"/>
        <item
                android:id="@+id/nav_settings"
                android:icon="@drawable/ic_settings_black_24dp"
                android:title="@string/settings"/>
    </group>

</menu>