forma do botão Flutter
shape: RoundedRectangleBorder(),
shape: BeveledRectangleBorder(),
shape: ContinuousRectangleBorder(),
shape: CircleBorder(),
Your CodeFu
shape: RoundedRectangleBorder(),
shape: BeveledRectangleBorder(),
shape: ContinuousRectangleBorder(),
shape: CircleBorder(),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Theme.of(context).primaryColor),
),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Colors.red)
),
RawMaterialButton(
...,
shape: CircleBorder(),
)