ReorderDragBoundaryProvider typedef

ReorderDragBoundaryProvider = DragBoundaryDelegate<Rect>? Function(BuildContext context)

Used to provide drag boundaries during drag-and-drop reordering.

link 
DragBoundary(
 child: CustomScrollView(
   slivers: <Widget>[
     SliverReorderableList(
       itemBuilder: (BuildContext context, int index) {
         return ReorderableDragStartListener(
           key: ValueKey<int>(index),
           index: index,
           child: Text('$index'),
         );
       },
       dragBoundaryProvider: (BuildContext context) {
         return DragBoundary.forRectOf(context);
       },
       itemCount: 5,
       onReorder: (int fromIndex, int toIndex) {},
     ),
   ],
 )
)

See also:

Implementation

typedef ReorderDragBoundaryProvider = DragBoundaryDelegate<Rect>? Function(BuildContext context);