Create a button with rounded border [duplicate]

How would you make a FlatButton into a button with a rounded border? I have the rounded border shape using RoundedRectangleBorder but somehow need to color the border.

new FlatButton(
  child: new Text("Button text),
  onPressed: null,
  shape: new RoundedRectangleBorder(borderRadius: new BorderRadius.circular(30.0))
)

Example of how button with rounded button would look :

Use OutlinedButton instead of FlatButton.

OutlinedButton(
  onPressed: null,
  style: ButtonStyle(
    shape: MaterialStateProperty.all(RoundedRectangleBorder(borderRadius: BorderRadius.circular(30.0))),
  ),
  child: const Text("Button text"),
);

FlatButton(
          onPressed: null,
          child: Text('Button', style: TextStyle(
              color: Colors.blue
            )
          ),
          textColor: MyColor.white,
          shape: RoundedRectangleBorder(side: BorderSide(
            color: Colors.blue,
            width: 1,
            style: BorderStyle.solid
          ), borderRadius: BorderRadius.circular(50)),
        )

Use StadiumBorder shape

OutlineButton( onPressed: () {}, child: Text("Follow"), borderSide: BorderSide(color: Colors.blue), shape: StadiumBorder(), )