title: Persistent draggable bottom sheet in Flutter
body: <p>I'm using <a href="https://pub.dev/packages/rubber" rel="nofollow noreferrer">Rubber</a> library at the moment, do you know an approach without using 3rd parts libraries?
  The Bottom Sheet must be persistent (not dismissable, not triggered by any button instead, always displayed) and draggable (It must be expanded and collapsed by dragging gestures)</p>