Flutter default font size

I found a better way for default font size by overriding the material text theme.

Reference: https://api.flutter.dev/flutter/material/TextTheme-class.html

For example: body1 is for normal Text widgets so for the red color to all Text widgets

 theme: ThemeData(
        textTheme: TextTheme(body1: TextStyle(backgroundColor: Colors.red))
      )

Result:

A Flutter theme defines not one, but many default font sizes. The size used depends on the situation, e.g. a Text widget would normally use body style, but the same widget would use button style if used inside of a button.

I found two ways to increase all font sizes across a Flutter application.

Simple solution: adjust the default theme

MaterialApp(
  theme: ThemeData(
    textTheme: Theme.of(context).textTheme.apply(
          fontSizeFactor: 1.1,
          fontSizeDelta: 2.0,
        ),
  ),
  ...
);

The resulting font size is (originalSize * fontSizeFactor + fontSizeDelta). So in the example above all font sizes are increased by 10% and then additionally by 2.

Solution with more control: define all sizes by hand

MaterialApp(
  theme: ThemeData(
    textTheme: TextTheme(
      bodyText1: TextStyle(fontSize: 18.0),
      bodyText2: TextStyle(fontSize: 16.0),
      button: TextStyle(fontSize: 16.0),
      ...  // and so on for every text style
    ),
  ),
  ...
);

The full list of styles can be found at https://api.flutter.dev/flutter/material/TextTheme-class.html.

You should prefer composition over inheritance.

class Mono12Text extends StatelessWidget {
  final String data;
  final TextAlign align;
  final TextStyle style;

  Mono12Text(
    this.data, {
    this.align,
    TextStyle style = const TextStyle(),
  }) : style = style.copyWith(
          fontFamily: 'Monospace',
          fontSize: 12,
        );

  @override
  Widget build(BuildContext context) {
    return Text(
      data,
      textAlign: align,
      style: style,
    );
  }
}