onUrlChanged always listen even I cancel the subscription & dispose the webview

I noticed that whenever I click the webview for the 2nd time . onUrlChanged listen ( duplicate ) the same data .

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`final flutterWebViewPlugin = FlutterWebviewPlugin();
StreamSubscription _onUrlChanged;

@override
void initState() {
super.initState();
flutterWebViewPlugin.close();
_onUrlChanged = flutterWebViewPlugin.onUrlChanged.listen((url) {
if (mounted) {
if (url.contains(
'${EnviromentConfig.baseUrl}/?status_id=1')) {
Uri uri = Uri.parse(url);
_redirect(uri);
} else if (url.contains(
'${EnviromentConfig.baseUrl}/?status_id=0')) {
Uri uri = Uri.parse(url);
String message = uri.queryParameters['message'].replaceAll('_', ' ');
Navigator.pop(_scaffoldKey.currentContext);
final snackBar =
SnackBar(backgroundColor: Colors.red, content: Text(message));
_scaffoldKey.currentState.showSnackBar(snackBar);
}
}
});
}

@override
void dispose() {
_onUrlChanged.cancel();
flutterWebViewPlugin.dispose();
super.dispose();
}`

Start with the onUrlChanged subscription and the dispose lifecycle shown in the report, then reproduce the second webview interaction using the supplied example. Trace whether cancellation and webview disposal stop callbacks; done means a later webview interaction does not deliver duplicate URL-change events.

Written by the indexing model from the issue text.