& drop documentation https://developer.android.com/guide/topics/ui/drag-drop - Build Apps for Foldable, Multi-Display, and Large-Screen Devices IO 2019 video https://www.youtube.com/watch?v=8uQEzv3upy8
Use it only when, ongoing conversations, important notifications !Users can opt-out. Make sure your bubble notification works as a normal notification as well. !Processes that are launched from a bubble stays in the bubbles (task stack). Keep it simple and task specific.
hidden View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION or //lay out for worst case the app can expect //as a continuous state View.SYSTEM_UI_FLAG_LAYOUT_STABLE or //lay out behind the status bar (optional) View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN