If you open Google Calendar on a phone running Android 10 (or later, presumably), you'll see the affordance for the ability to swipe up from the bottom of the screen is still there as a grey bar, but it's rendered over the top of the activity itself.
On my own app, however, this navigation bar at the bottom (if indeed that's what it is) has a grey background and my activity presumably stops at the top of it.
How do I do what Google Calendar has done?
add this line to your app theme:
<item name="android:statusBarColor">@color/colorPrimary</item>
like:
<style name="MainActivityTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
<item name="android:statusBarColor">@color/colorPrimary</item>
<item name="android:windowLightStatusBar" tools:ignore="NewApi">false</item>
</style>