In flutter, first I declare the varibale(late final WebViewController webViewController_;)
and then execute webViewController_.runJavaScript("localStorage.setItem('test_val','test_val__')"); this code.
But runJavaScript doesn’t run. I tried another function that is included in webViewController(forexample clearLocalStorage, clearCache .. ) but all of this code also doesn’t run..

I think type(late final) cause the problem but I can’t convince.

So I wan’t to ask which code cause the problem in my code

The structure of code like this (code below)

import 'package:webview_flutter/webview_flutter.dart';
...

void main() async {
...
}

class TestApp extends StatelessWidget {
  const TestApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      initialRoute: '/',
      routes: {
        '/': (context) => const TestPage(),
      },
    );
  }
}
class TestPage extends StatefulWidget {
  const TestPage({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() => _TESTPageState();
}

class _TESTPageState extends State<TMSPage> with WidgetsBindingObserver{
  late final WebViewController webViewController_;
  @override
  void initState(){
    super.initState();
  }
  ...
  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      print('in1'); // operated
      // Below code occur the problem
      webViewController_.runJavaScript("localStorage.setItem('test_val','test_val__')");
      print('in2'); // not operated, not error occured, but progress is stop
      return false;     
    },
    child: Scaffold(
      body: Center(
        child: FutureBuilder<bool?>(
          future: checkLogin(),
          builder: (context, snapshot) {
            if(Platform.isAndroid) {
              if (snapshot.data == true) {
                return const WebViewPage();  
              }else {
                return SignIn(); 
              }
            }else if(Platform.isIOS){
              if (snapshot.data == true) {
                return const WebViewPage();
              }else if (snapshot.data == null) {
                return SignIn(); 
              }else{
                return const NullPage();
              }
            }else{
              return const NullPage();
            }


          },
        ),
      ),
    ),
    );
  }
}