How to check if Android or iOS dark mode is enabled in Flutter?

There are 2 ways:

1. NO context needed, you can use it in initState:

   var brightness = SchedulerBinding.instance.window.platformBrightness;
   bool darkModeOn = brightness == Brightness.dark;
   

2. context is needed:

   var brightness = MediaQuery.of(context).platformBrightness;
   bool darkModeOn = brightness == Brightness.dark;
   

If you define a dark theme in your MaterialApp, your app will automatically go dark when Android Q dark theme is enabled. You have to specify your dark theme like this:

MaterialApp(
  theme: ThemeData(
    brightness: Brightness.light,
    primaryColor: Colors.red,
  ),
  darkTheme: ThemeData(
    brightness: Brightness.dark,
  ),
);

According to this medium article,

Now when you toggle Dark Theme in your system drawer, your Flutter app will automatically switch from your regular theme to your darkTheme!

However, if you want to manually check whether you're on dark mode, you can easily write a method using the Platform Channel API. More details here. As for the native code, check here.

I found the way. Here it is.

  bool _darkModeEnabled = false;

  void _checkIfDarkModeEnabled() {
    final ThemeData theme = Theme.of(context);
    theme.brightness == appDarkTheme().brightness
        ? _darkModeEnabled = true
        : _darkModeEnabled = false;
  }