The following animation shows the app’s behavior:

This recipe begins with a prebuilt list of menu items and
a row of customers.
The first step is to recognize a long press
and display a draggable photo of a menu item.

Press and drag

Flutter provides a widget called LongPressDraggable
that provides the exact behavior that you need to begin
a drag-and-drop interaction. A LongPressDraggable
widget recognizes when a long press occurs and then 
displays a new widget near the user’s finger.
As the user drags, the widget follows the user’s finger.
LongPressDraggable gives you full control over the 
widget that the user drags.

Each menu list item is displayed with a custom
MenuListItem widget.

Wrap the MenuListItem widget with a LongPressDraggable widget.