Flutter ColorScheme CopyWith brightness not working - flutter

Question

In my Flutter project app_theme.dart file I have this code:
class AppTheme {
static const primaryColor = Color.fromARGB(255, 106, 49, 185);
static ThemeData lightTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: ColorScheme.fromSeed(
seedColor: primaryColor,
brightness: Brightness.light,
),
);
}
static ThemeData darkTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: ColorScheme.fromSeed(
seedColor: primaryColor,
brightness: Brightness.dark,
),
);
}
Then in main.dart, my Material App widget implements this like so:
theme: AppTheme.lightTheme(),
darkTheme: AppTheme.darkTheme(),
This works correctly, so that in the Android emulator, when I switch between dark and light mode (within settings), the app automatically changes.
But what I wanted to do was declare the ColorScheme separately (so I can override certain colors etc) and then just use copyWith to declare the brightness in the ThemeData:
class AppTheme {
static const primaryColor = Color.fromARGB(255, 106, 49, 185);
static ColorScheme colorScheme = ColorScheme.fromSeed(
seedColor: primaryColor,
// Customisation goes here
);
static ThemeData lightTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: colorScheme.copyWith(
brightness: Brightness.light,
),
);
}
static ThemeData darkTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: colorScheme.copyWith(
brightness: Brightness.dark,
),
);
}
But this does not work. It just stays in light mode all the time, although no errors are thrown.
Any ideas what I'm doing wrong?

Answer 1

ColorScheme.fromSeed constructor generates a ColorScheme derived from the given seedColor. Copying the generated object obviously does not generate colours again. Something like this would work:
class AppTheme {
static const primaryColor = Color.fromARGB(255, 106, 49, 185);
static ColorScheme fromBrightness({required Brightness brightness}) {
return ColorScheme.fromSeed(
brightness: brightness,
seedColor: primaryColor,
// Customisation goes here
);
}
static ThemeData lightTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: AppTheme.fromBrightness(
brightness: Brightness.light,
),
);
}
static ThemeData darkTheme() {
return ThemeData(
useMaterial3: true,
colorScheme: AppTheme.fromBrightness(
brightness: Brightness.dark,
),
);
}
}