checked connectivity using webview pages in flutter

Please I want to make my own page if the connection is lost in flutter and I don’t know how to do it please can someone help me this is my code I tried many ways and it doesn’t work.
I need to remove the page of WebPage doesn’t work and design my own one please I’m working on a project

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with TickerProviderStateMixin{

  final Completer<WebViewController> _controller =
  Completer<WebViewController>();

  late WebViewController _webViewController;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Welcome to Flutter',
      home: SafeArea(
        child : Scaffold(
          body: WebView(
            initialUrl: "https://wikoget.com",
            javascriptMode: JavascriptMode.unrestricted,
            onWebViewCreated: (WebViewController webViewController) {
              _webViewController = webViewController;
              _controller.complete(webViewController);
            },
            onPageFinished: (String url) {
              _webViewController
                  .evaluateJavascript("javascript:(function() { " +
                  "var head = document.getElementsByClassName('main-header-bar-wrap')[0];" +
                  "head.parentNode.style.cssText = ' position: sticky;position: -webkit-sticky; top : 0 ';" +

                  "var footer = document.getElementsByTagName('footer')[0];" +
                  "footer.parentNode.removeChild(footer);" +
                  "})()")
                  .then((value) => debugPrint('Page finished loading Javascript'))
                  .catchError((onError) => debugPrint('$onError'));
            },
            gestureNavigationEnabled: true,
          ),
        ),
      ),
    );
  }

  JavascriptChannel _toasterJavascriptChannel(BuildContext context) {
    return JavascriptChannel(
        name: 'Toaster',
        onMessageReceived: (JavascriptMessage message) {
          // ignore: deprecated_member_use
          Scaffold.of(context).showSnackBar(
            SnackBar(content: Text(message.message)),
          );
        });
  }
}