why the switch between dark mode and light mode isn't run by flutter I used BlocProvider and BlocConsumer .Is null safety prevent it?

main function the main problem the condition in ThemeMode isn't execute except true

Widget build(BuildContext context) {
return BlocProvider(
  create: (context)=>AppCubit(),
  child: BlocConsumer<AppCubit,Appstates>(
    listener: (BuildContext context,state){
      if(state is AppGetMode)
        {
          print(AppCubit.get(context).isDark);
        }
    },
    builder: (context,state) {
      return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme:ThemeData(
        primarySwatch: Colors.deepOrange,
        scaffoldBackgroundColor: Colors.white,
          appBarTheme: AppBarTheme(
          titleSpacing: 20.0,
          backwardsCompatibility: false,

          backgroundColor: Colors.white,
          elevation: 0.0,
          titleTextStyle: TextStyle(
            color: Colors.black,
            fontSize: 20.0,
            fontWeight: FontWeight.bold,
          ),
          
       
      ),
      darkTheme:ThemeData(
        primarySwatch: Colors.deepOrange,
        scaffoldBackgroundColor: Colors.grey,
        appBarTheme: AppBarTheme(
          titleSpacing: 20.0,

          elevation: 0.0,
          titleTextStyle: TextStyle(
            color: Colors.white,
            fontSize: 20.0,
            fontWeight: FontWeight.bold,
          ),
          iconTheme: IconThemeData(
            color: Colors.white,
          ),
        ),
        floatingActionButtonTheme: FloatingActionButtonThemeData(
          backgroundColor: Colors.deepOrange,
        ),
       
      
        ),
      ),

      themeMode:AppCubit.get(context).isDark ? ThemeMode.dark:ThemeMode.light,
      home: Navigation(),
    );
    },
  ),
);
}

The error in ThemeMode it's Not change when i press on Icon Button and the Theme is always light AppCubit Function to change mode by bool true is Dark false is Light The blocConsume an BlocProvider is running in more than screen

true is Dark false is Light

iconButton with onpressed

Padding(
                padding:  EdgeInsets.all(8.0),
                child: IconButton(onPressed: () {AppCubit.get(context).modeAppNews();}, icon:  const Icon(Icons.dark_mode_outlined) )                               
   )