Creating Options Menu with Sub Items - Android Studio Tutorial

Step 1

1. Go to res -> drawable -> New -> Vector Asset -> Select Menu Icon -> Give it suitable name
2. res -> new -> Android Resource Directory 
1. Select Resource Type = Menu
2. Give a suitable name, we used topnav_menu
3.  Add Menu Items to topnav_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/item1"
    android:icon="@drawable/ic_right_arrow"
    android:title="Item 1"
    app:showAsAction="never">
</item>
    <item android:id="@+id/item2"
        android:icon="@drawable/ic_right_arrow"
        android:title="Item 2"
        app:showAsAction="never">
    </item>

    <item android:id="@+id/item3"
        android:icon="@drawable/ic_right_arrow"
        android:title="Item 3"
        app:showAsAction="never">
    </item>
</menu>

4. Add following functions in MainActivity.java file

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.topnav_menu, menu);
    return true; /* super.onCreateOptionsMenu(menu); */
}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {

    switch (item.getItemId()) {
        case R.id.item1:
             Toast.makeText(this,"Item 1 Selected", Toast.LENGTH_SHORT ).show();
             return true;
        case R.id.item2:
            Toast.makeText(this,"Item 2 Selected", Toast.LENGTH_SHORT ).show();
            return true;
        case R.id.item3:
            Toast.makeText(this,"Item 3 Selected", Toast.LENGTH_SHORT ).show();
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }

}
5. Build & Run your App.
6. You are done.

Here is the complete Video Guide on Creating Menu.