Can't change the status bar Icon Brightness in flutter app?

Question

In main.dart

void main() {
SystemChrome.setSystemUIOverlayStyle(
SystemUiOverlayStyle(
  statusBarColor: Colors.black.withOpacity(0), //top bar color
  statusBarIconBrightness: Brightness.dark, //top bar icons
  systemNavigationBarColor: Colors.black, //bottom bar color
  systemNavigationBarIconBrightness: Brightness.light, //bottom bar icons
),
);
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
 Widget build(BuildContext context) {
return MaterialApp(
  theme: ThemeData(
    //primaryColor: Color.fromRGBO(113, 201, 206, 1),
    fontFamily: 'Montserrat',
    textTheme: TextTheme(
      headline: TextStyle(
        fontSize: 40,
        fontWeight: FontWeight.w500,
      ),
      title: TextStyle(
        fontWeight: FontWeight.w700,
        fontSize: 16,
      ),
      body1: TextStyle(
        fontSize: 12,
      ),
    ),
  ),
  home: Test(),
  routes: {
    MainScreen.routeName: (context) => MainScreen(),
  },
);
}
}

I am using the above code to change the color of the status bar, statusBarIconBrightness: Brightness.dark has no effect. It becomes black but after a few seconds it switches back to `Brightness.light'. What's wrong?

Running on Android Emulator. I don't want to have appBar int the Test() widget.

Solution

That's because you're not explicitly changing AppBar's brightness in your Test page. Run this code and see the difference:

void main() {
  SystemChrome.setSystemUIOverlayStyle(
    SystemUiOverlayStyle(
      statusBarColor: Colors.black.withOpacity(0), //top bar color
       // statusBarIconBrightness: Brightness.dark, // don't use this
    ),
  );
  runApp(MyApp2());
}
class MyApp2 extends StatelessWidget {
// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("AppBar"),
          brightness: Brightness.light, // use this instead
        ),
      ),
    );
  }
}

Output-1 (Brightness.dark):

Output-2 (Brightness.light):