To preserve the original buttons’ appearance in these cases, one can
define button styles that match the original as closely as you
like. For example, the following style makes a TextButton look
like a default FlatButton:

final

ButtonStyle

flatButtonStyle

TextButton

styleFrom

primary:

Colors

black87

minimumSize:

Size

88

36

),

padding:

EdgeInsets

symmetric

horizontal:

16.0

),

shape:

const

RoundedRectangleBorder

borderRadius:

BorderRadius

all

Radius

circular

2.0