CODE EXAMPLE FOR DART

change font size in flutter

new MaterialButton(
  height: 140.0,
  minWidth: double.infinity,
  color: Theme.of(context).primaryColor,
  textColor: Colors.white,
  child: new Text(
    "material button",
    style: new TextStyle(
      fontSize: 20.0,
      color: Colors.yellow,
    ),
  ),
  onPressed: () => {},
  splashColor: Colors.redAccent,
);