Zwiększ wysokość dolnego trumienia arkusza

showModalBottomSheet<dynamic>(
isScrollControlled: true,
context: context,
builder: (BuildContext bc) {
  return Wrap(
      children: <Widget>[
          Container(
                 child: Container(
                  decoration: new BoxDecoration(
                    color: forDialog ? Color(0xFF737373) : Colors.white,
                    borderRadius: new BorderRadius.only(
                          topLeft: const Radius.circular(25.0),
                          topRight: const Radius.circular(25.0))),
                    child: yourWidget(),
                 ),
              )
      ]
   )
 }
)
Alexander Ibekason