Can't get keyboard to appear over bottom navigation

In [the Material Design guidelines](https://material.io/guidelines/components/bottom-navigation.html#bottom-navigation-specs), it says:

> Bottom sheets and keyboards appear in front of the bottom nav bar, temporarily covering it.

(There's quite a nice video in the "elevation" section, where a "bottom sheet" covers the bottom navigation.)

How should this work in general? It doesn't seem supported by default - when I add an `EditText` to one a fragment, the bottom navigation bar does not hide when the keyboard appears.

### Additional complications in my case.

In my specific case, I have the following other requirements:
1. The content view can contain stuff like `ScrollView`s, so I think I need to use [`adjustResize`](https://developer.android.com/guide/topics/manifest/activity-element.html#wsoft) in the activity's manifest entry (`adjustPan` would not interact well with the scrolling).
2. The bottom navigation should not disappear when scrolling (it should always be showing).

To try to avoid the X-Y problem, I'll stop here, and post what I've tried so far as a comment.

Start by reproducing the reported case: place an EditText in a fragment, include possible ScrollViews, and use adjustResize in the activity manifest. Compare the result with the Material Design behavior described in the issue; done means the keyboard can cover the bottom navigation while the navigation remains visible during scrolling.

Written by the indexing model from the issue text.