material-components_material-components-flutter/docs/components/dartpad/bottom_sheets/theme/main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Standard Bottom Sheet Demo',
      theme: _buildShrineTheme(),
      home: Scaffold(
        // Use a Builder to get a context within the Scaffold.
        body: Builder(
          builder: (context) {
            return Center(
              child: TextButton(
                child: Text('SHOW BOTTOM SHEET'),
                onPressed: () {
                  showBottomSheet(
                    context: context,
                    builder: (context) {
                      final theme = Theme.of(context);
                      // Using Wrap makes the bottom sheet height the height of the content.
                      // Otherwise, the height will be half the height of the screen.
                      return Wrap(
                        children: [
                          ListTile(
                            title: Text(
                              'Header',
                              style: theme.textTheme.subtitle1
                                  .copyWith(color: theme.colorScheme.onPrimary),
                            ),
                            tileColor: theme.colorScheme.primary,
                          ),
                          ListTile(
                            title: Text('Title 1'),
                          ),
                          ListTile(
                            title: Text('Title 2'),
                          ),
                          ListTile(
                            title: Text('Title 3'),
                          ),
                          ListTile(
                            title: Text('Title 4'),
                          ),
                          ListTile(
                            title: Text('Title 5'),
                          ),
                        ],
                      );
                    },
                  );
                },
              ),
            );
          },
        ),
      ),
    );
  }
}

IconThemeData _customIconTheme(IconThemeData original) {
  return original.copyWith(color: shrineBrown900);
}

ThemeData _buildShrineTheme() {
  final ThemeData base = ThemeData.light();
  return base.copyWith(
    colorScheme: _shrineColorScheme,
    accentColor: shrineBrown900,
    primaryColor: shrinePink100,
    buttonColor: shrinePink100,
    scaffoldBackgroundColor: shrineBackgroundWhite,
    cardColor: shrineBackgroundWhite,
    textSelectionTheme: TextSelectionThemeData(selectionColor: shrinePink100),
    errorColor: shrineErrorRed,
    buttonTheme: const ButtonThemeData(
      colorScheme: _shrineColorScheme,
      textTheme: ButtonTextTheme.normal,
    ),
    primaryIconTheme: _customIconTheme(base.iconTheme),
    textTheme: _buildShrineTextTheme(base.textTheme),
    primaryTextTheme: _buildShrineTextTheme(base.primaryTextTheme),
    accentTextTheme: _buildShrineTextTheme(base.accentTextTheme),
    iconTheme: _customIconTheme(base.iconTheme),
  );
}

TextTheme _buildShrineTextTheme(TextTheme base) {
  return base
      .copyWith(
        headline5: base.headline5.copyWith(
          fontWeight: FontWeight.w500,
          letterSpacing: defaultLetterSpacing,
        ),
        headline6: base.headline6.copyWith(
          fontSize: 18,
          letterSpacing: defaultLetterSpacing,
        ),
        caption: base.caption.copyWith(
          fontWeight: FontWeight.w400,
          fontSize: 14,
          letterSpacing: defaultLetterSpacing,
        ),
        bodyText1: base.bodyText1.copyWith(
          fontWeight: FontWeight.w500,
          fontSize: 16,
          letterSpacing: defaultLetterSpacing,
        ),
        bodyText2: base.bodyText2.copyWith(
          letterSpacing: defaultLetterSpacing,
        ),
        subtitle1: base.subtitle1.copyWith(
          letterSpacing: defaultLetterSpacing,
        ),
        headline4: base.headline4.copyWith(
          letterSpacing: defaultLetterSpacing,
        ),
        button: base.button.copyWith(
          fontWeight: FontWeight.w500,
          fontSize: 14,
          letterSpacing: defaultLetterSpacing,
        ),
      )
      .apply(
        fontFamily: 'Rubik',
        displayColor: shrineBrown900,
        bodyColor: shrineBrown900,
      );
}

const ColorScheme _shrineColorScheme = ColorScheme(
  primary: shrinePink100,
  primaryVariant: shrineBrown900,
  secondary: shrinePink50,
  secondaryVariant: shrineBrown900,
  surface: shrineSurfaceWhite,
  background: shrineBackgroundWhite,
  error: shrineErrorRed,
  onPrimary: shrineBrown900,
  onSecondary: shrineBrown900,
  onSurface: shrineBrown900,
  onBackground: shrineBrown900,
  onError: shrineSurfaceWhite,
  brightness: Brightness.light,
);

const Color shrinePink50 = Color(0xFFFEEAE6);
const Color shrinePink100 = Color(0xFFFEDBD0);
const Color shrinePink300 = Color(0xFFFBB8AC);
const Color shrinePink400 = Color(0xFFEAA4A4);

const Color shrineBrown900 = Color(0xFF442B2D);
const Color shrineBrown600 = Color(0xFF7D4F52);

const Color shrineErrorRed = Color(0xFFC5032B);

const Color shrineSurfaceWhite = Color(0xFFFFFBFA);
const Color shrineBackgroundWhite = Colors.white;

const defaultLetterSpacing = 0.03;