flutter button style

ElevatedButton(
  style: ButtonStyle(
    backgroundColor: MaterialStateProperty.resolveWith<Color>(
      (Set<MaterialState> states) {
        if (states.contains(MaterialState.pressed))
          return Theme.of(context).colorScheme.primary.withOpacity(0.5);
        return null; // Use the component's default.
      },
    ),
  ),
)