Which all fonts are supported by Flutter without requiring external import?

Question

Text(
    'Sample',
    style: TextStyle(
        fontFamily: '',
    ), // TextStyle
), //Text

What all values can I give to the fontFamily attribute without downloading external fonts ?

Answer 1

Having looked at material/typography.dart you should be able to find out:

For Android and default to MaterialApp

The default font of MaterialApp is roboto, a Google font.

 /// A material design text theme with dark glyphs based on Roboto.
  ///
  /// This [TextTheme] provides color but not geometry (font size, weight, etc).
  static const TextTheme blackMountainView = TextTheme(
    display4   : TextStyle(debugLabel: 'blackMountainView display4',   fontFamily: 'Roboto', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display3   : TextStyle(debugLabel: 'blackMountainView display3',   fontFamily: 'Roboto', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display2   : TextStyle(debugLabel: 'blackMountainView display2',   fontFamily: 'Roboto', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display1   : TextStyle(debugLabel: 'blackMountainView display1',   fontFamily: 'Roboto', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    headline   : TextStyle(debugLabel: 'blackMountainView headline',   fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    title      : TextStyle(debugLabel: 'blackMountainView title',      fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    subhead    : TextStyle(debugLabel: 'blackMountainView subhead',    fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    body2      : TextStyle(debugLabel: 'blackMountainView body2',      fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    body1      : TextStyle(debugLabel: 'blackMountainView body1',      fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    caption    : TextStyle(debugLabel: 'blackMountainView caption',    fontFamily: 'Roboto', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    button     : TextStyle(debugLabel: 'blackMountainView button',     fontFamily: 'Roboto', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    subtitle   : TextStyle(debugLabel: 'blackMountainView subtitle',   fontFamily: 'Roboto', inherit: true, color: Colors.black,   decoration: TextDecoration.none),
    overline   : TextStyle(debugLabel: 'blackMountainView overline',   fontFamily: 'Roboto', inherit: true, color: Colors.black,   decoration: TextDecoration.none),
  );

  /// A material design text theme with light glyphs based on Roboto.
  ///
  /// This [TextTheme] provides color but not geometry (font size, weight, etc).
  static const TextTheme whiteMountainView = TextTheme(
    display4   : TextStyle(debugLabel: 'whiteMountainView display4',   fontFamily: 'Roboto', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display3   : TextStyle(debugLabel: 'whiteMountainView display3',   fontFamily: 'Roboto', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display2   : TextStyle(debugLabel: 'whiteMountainView display2',   fontFamily: 'Roboto', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display1   : TextStyle(debugLabel: 'whiteMountainView display1',   fontFamily: 'Roboto', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    headline   : TextStyle(debugLabel: 'whiteMountainView headline',   fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    title      : TextStyle(debugLabel: 'whiteMountainView title',      fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    subhead    : TextStyle(debugLabel: 'whiteMountainView subhead',    fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    body2      : TextStyle(debugLabel: 'whiteMountainView body2',      fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    body1      : TextStyle(debugLabel: 'whiteMountainView body1',      fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    caption    : TextStyle(debugLabel: 'whiteMountainView caption',    fontFamily: 'Roboto', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    button     : TextStyle(debugLabel: 'whiteMountainView button',     fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    subtitle   : TextStyle(debugLabel: 'whiteMountainView subtitle',   fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    overline   : TextStyle(debugLabel: 'whiteMountainView overline',   fontFamily: 'Roboto', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
  );

and for iOS if using Curpertino it would be .SF UI Display default ios font.

 /// A material design text theme with dark glyphs based on San Francisco.
  ///
  /// This [TextTheme] provides color but not geometry (font size, weight, etc).
  static const TextTheme blackCupertino = TextTheme(
    display4   : TextStyle(debugLabel: 'blackCupertino display4',   fontFamily: '.SF UI Display', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display3   : TextStyle(debugLabel: 'blackCupertino display3',   fontFamily: '.SF UI Display', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display2   : TextStyle(debugLabel: 'blackCupertino display2',   fontFamily: '.SF UI Display', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    display1   : TextStyle(debugLabel: 'blackCupertino display1',   fontFamily: '.SF UI Display', inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    headline   : TextStyle(debugLabel: 'blackCupertino headline',   fontFamily: '.SF UI Display', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    title      : TextStyle(debugLabel: 'blackCupertino title',      fontFamily: '.SF UI Display', inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    subhead    : TextStyle(debugLabel: 'blackCupertino subhead',    fontFamily: '.SF UI Text',    inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    body2      : TextStyle(debugLabel: 'blackCupertino body2',      fontFamily: '.SF UI Text',    inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    body1      : TextStyle(debugLabel: 'blackCupertino body1',      fontFamily: '.SF UI Text',    inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    caption    : TextStyle(debugLabel: 'blackCupertino caption',    fontFamily: '.SF UI Text',    inherit: true, color: Colors.black54, decoration: TextDecoration.none),
    button     : TextStyle(debugLabel: 'blackCupertino button',     fontFamily: '.SF UI Text',    inherit: true, color: Colors.black87, decoration: TextDecoration.none),
    subtitle   : TextStyle(debugLabel: 'blackCupertino subtitle',   fontFamily: '.SF UI Text',    inherit: true, color: Colors.black,   decoration: TextDecoration.none),
    overline   : TextStyle(debugLabel: 'blackCupertino overline',   fontFamily: '.SF UI Text',    inherit: true, color: Colors.black,   decoration: TextDecoration.none),
  );

  /// A material design text theme with light glyphs based on San Francisco.
  ///
  /// This [TextTheme] provides color but not geometry (font size, weight, etc).
  static const TextTheme whiteCupertino = TextTheme(
    display4   : TextStyle(debugLabel: 'whiteCupertino display4',   fontFamily: '.SF UI Display', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display3   : TextStyle(debugLabel: 'whiteCupertino display3',   fontFamily: '.SF UI Display', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display2   : TextStyle(debugLabel: 'whiteCupertino display2',   fontFamily: '.SF UI Display', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    display1   : TextStyle(debugLabel: 'whiteCupertino display1',   fontFamily: '.SF UI Display', inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    headline   : TextStyle(debugLabel: 'whiteCupertino headline',   fontFamily: '.SF UI Display', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    title      : TextStyle(debugLabel: 'whiteCupertino title',      fontFamily: '.SF UI Display', inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    subhead    : TextStyle(debugLabel: 'whiteCupertino subhead',    fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    body2      : TextStyle(debugLabel: 'whiteCupertino body2',      fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    body1      : TextStyle(debugLabel: 'whiteCupertino body1',      fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    caption    : TextStyle(debugLabel: 'whiteCupertino caption',    fontFamily: '.SF UI Text',    inherit: true, color: Colors.white70, decoration: TextDecoration.none),
    button     : TextStyle(debugLabel: 'whiteCupertino button',     fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    subtitle   : TextStyle(debugLabel: 'whiteCupertino subtitle',   fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
    overline   : TextStyle(debugLabel: 'whiteCupertino overline',   fontFamily: '.SF UI Text',    inherit: true, color: Colors.white,   decoration: TextDecoration.none),
  );

So, you should be able to retrieve the font family by the following code

DefaultTextStyle.of(context).style.fontFamily

Therefore, you can reuse the same font as you retrieve.