getThemeData method Null safety

Implementation

static ThemeData getThemeData(
  final Brightness brightness,
  final String colorTag,
) {
  ColorScheme myColorScheme;
  if (brightness == Brightness.dark) {
    myColorScheme = const ColorScheme.dark();
  } else {
    final MaterialColor materialColor =
        MATERIAL_COLORS[colorTag] ?? MATERIAL_COLORS[COLOR_TAG_BLUE]!;
    myColorScheme = ColorScheme.light(
      primary: materialColor[600]!,
      primaryContainer: materialColor[900],
    );
  }

  return ThemeData(
    colorScheme: myColorScheme,
    bottomNavigationBarTheme: BottomNavigationBarThemeData(
      selectedItemColor: myColorScheme.onSurface,
      unselectedItemColor: myColorScheme.onSurface,
    ),
    textTheme: _TEXT_THEME,
    floatingActionButtonTheme: FloatingActionButtonThemeData(
      backgroundColor: myColorScheme.secondary,
      foregroundColor: myColorScheme.onSecondary,
    ),
    appBarTheme: AppBarTheme(
      color: brightness == Brightness.dark ? null : myColorScheme.primary,
    ),
    toggleableActiveColor: myColorScheme.primary,
  );
}