I want to use the WebView in Flutter to load a code redemption page from apple, so that my user can use discounts on subscriptions. For example pages like Google, Flutter.dev, … it works fine, but using the url from apple sadly won’t. I just get a blank white screen in my body – the appbar works fine. What could be wrong?

import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:webview_flutter/webview_flutter.dart';
import '../../configuration/theme.dart';


class FumiProPromoPage extends StatefulWidget {
  String code;
  //Variable Code übergeben
  FumiProPromoPage({
    Key? key,
    required this.code,
  }) : super(key: key);

  @override
  State<FumiProPromoPage> createState() => _FumiProPromoPageState();
}

class _FumiProPromoPageState extends State<FumiProPromoPage> {
  var loadingPercentage = 0;
  late WebViewController controller;
  final GlobalKey webViewKey = GlobalKey();

  String promourl = "https://google.de";
  String url = "";
  double progress = 0;
  final urlController = TextEditingController();


  @override
  void initState() {
    super.initState();
    promourl = 'https://apps.apple.com/redeem?ctx=offercodes&id=1567964963&code=${widget.code}';
    print(promourl);

    controller = WebViewController()
    ..setJavaScriptMode(JavaScriptMode.unrestricted)
    ..setBackgroundColor(const Color(0x00000000))
    ..setNavigationDelegate(
      NavigationDelegate(
        onProgress: (int progress) {
          // Update loading bar.
        },
        onPageStarted: (String url) {},
        onPageFinished: (String url) {},
        onWebResourceError: (WebResourceError error) {},
        onNavigationRequest: (NavigationRequest request) {
          if (request.url.startsWith('https://www.youtube.com/')) {
            return NavigationDecision.prevent;
          }
          return NavigationDecision.navigate;
        },
      ),
    )
    ..loadRequest(Uri.parse(promourl));
  }
  Widget build(BuildContext context) {
    
    return Scaffold(
      appBar: AppBar(
            elevation: 0,
            backgroundColor: fumigruenAccent,
            title: const Text(
              "Promocode einlösen",
              style: TextStyle(
                color: Colors.black,
              ),
            ),
            leading: CloseButton(
              color: Colors.black,
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),),
        
        
      body: 
      
      Stack(
        children: [
          WebViewWidget(
            controller: controller,
          ), 
          
          loadingPercentage < 100
              ? LinearProgressIndicator(
                  color: Colors.red,
                  value: loadingPercentage / 100.0,
                )
              : Container()
        ],
      ), 
    );
  }
}

I also deactivated the Apple Transport Security (ATS) feature for http requests to figure out if that’s the problem. It sadly didn’t work.

To do this I added the following lines to my Info.plist

<key>NSAppTransportSecurity</key>
<dict>
  <key>NSAllowsArbitraryLoads</key><true/>
</dict>

Any ideas? many thanks in advance!