Answers for "flutter shape border circle"

rounded raisedbutton in flutter

RaisedButton(
                onPressed: () {},
                color: Colors.amber,
                shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(10)),
                child: Text("Click This"),
              )

using shape property in flutter for circular corner

shape: RoundedRectangleBorder(
  borderRadius: BorderRadius.circular(18.0),
  side: BorderSide(color: Colors.red)
),