ReorderItemProxyDecorator typedef Null safety
child will be the item that is being dragged, and
index is the
position of the item in the list.
animation will be driven forward from 0.0 to 1.0 while the item is
being picked up during a drag operation, and reversed from 1.0 to 0.0 when
the item is dropped. This can be used to animate properties of the proxy
like an elevation or border.
The returned value will typically be the
child wrapped in other widgets.
typedef ReorderItemProxyDecorator = Widget Function(Widget child, int index, Animation<double> animation);