All the solution above are not really working without some minor artifacts or issues (e.g. missing ripple effect, unwanted borders, not respecting the theme’s minWidth for buttons).
The solution below has none of the above issues (the critical part is to use the Ink
widget to retain the ripple capabilities over the gradient):
RaisedButton(
onPressed: () { },
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(80.0)),
padding: const EdgeInsets.all(0.0),
child: Ink(
decoration: const BoxDecoration(
gradient: myGradient,
borderRadius: BorderRadius.all(Radius.circular(80.0)),
),
child: Container(
constraints: const BoxConstraints(minWidth: 88.0, minHeight: 36.0), // min sizes for Material buttons
alignment: Alignment.center,
child: const Text(
'OK',
textAlign: TextAlign.center,
),
),
),
)