Answers for "how to make border radius in elevated app button"

flutter elevated button radius

style: ButtonStyle(
  shape: MaterialStateProperty.all<RoundedRectangleBorder>(
    RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(18.0),
      side: BorderSide(color: Colors.red)
    )
  )
)

rounded ElevatedButton

ElevatedButton(
  onPressed: () {},
  child: Text('Button'),
  style: ElevatedButton.styleFrom(shape: StadiumBorder()),
)
Using RoundedRectangleBorder

ElevatedButton(
  onPressed: () {},
  child: Text('Button'),
  style: ElevatedButton.styleFrom(
    shape: RoundedRectangleBorder(
      borderRadius: BorderRadius.circular(12), // <-- Radius
    ),
  ),
)
Using CircleBorder

ElevatedButton(
  onPressed: () {},
  child: Text('Button'),
  style: ElevatedButton.styleFrom(
    shape: CircleBorder(),
    padding: EdgeInsets.all(24),
  ),
)
Using BeveledRectangleBorder

ElevatedButton(
  onPressed: () {},
  child: Text('Button'),
  style: ElevatedButton.styleFrom(
    shape: BeveledRectangleBorder(
      borderRadius: BorderRadius.circular(12)
    ),
  ),
)
OutlinedButton
Using StadiumBorder

OutlinedButton(
  onPressed: () {},
  child: Text('Button'),
  style: OutlinedButton.styleFrom(
    shape: StadiumBorder(),
  ),
)
Using RoundedRectangleBorder

OutlinedButton(
  onPressed: () {},
  child: Text('Button'),
  style: OutlinedButton.styleFrom(
    shape: BeveledRectangleBorder(
      borderRadius: BorderRadius.circular(12),
    ),
  ),
)
Using CircleBorder:

OutlinedButton(
  onPressed: () {},
  child: Text('Button'),
  style: OutlinedButton.styleFrom(
    shape: CircleBorder(),
    padding: EdgeInsets.all(24),
  ),
)
Using BeveledRectangleBorder

OutlinedButton(
  onPressed: () {},
  child: Text('Button'),
  style: OutlinedButton.styleFrom(
    shape: BeveledRectangleBorder(
      borderRadius: BorderRadius.circular(12),
    ),
  ),
)