a> and
does not add a back button to the enclosing Scaffold's app bar, use the
<a href="https://api.flutter.dev/flutter/material/Scaffold/bottomSheet.html">Scaffold.bottomSheet</a> constructor parameter.</p>
<p>A persistent bottom sheet shows information that supplements the primary
content of the app. A persistent bottom sheet remains visible even when
the user interacts with other parts of the app.</p>
<p>A closely related widget is a modal bottom sheet, which is an alternative
to a menu or a dialog and p