FlatButton({Key key, @required VoidCallback onPressed, Color textColor, Color disabledTextColor, Color color, Color disabledColor, ButtonTextTheme textTheme, Brightness colorBrightness, Widget child })

Creates a flat button.

The child argument is required and is typically a Text widget in all caps.

Source 

FlatButton({
  Key key,
  @required this.onPressed,
  this.textColor,
  this.disabledTextColor,
  this.color,
  this.disabledColor,
  this.textTheme,
  this.colorBrightness,
  this.child
}) : super(key: key) {
  assert(child != null);
}