WebViewScaffold should extend Scaffold, else snackbars, alertdialogs etc cannot be used.

[MaskyS]

While using Widget Webview, it is not possible to show AlertDialogs or SnackBars or ModalBottomSheets.

For instance, to show a snackbar, we'd either use Scaffold.of(context).showSnackBar(new SnackBar(...)...); or the method below:

              return new WebviewScaffold(
                key: _webViewScaffoldKey,
                userAgent: userAgentString,
                url: _getSubjectUrl(value),
                appBar: new StudentoAppBar(actions: <Widget>[
                  new IconButton(
                    icon: new Icon(Icons.file_download),
                    color: Colors.white,
                    onPressed: () {
                      _webViewScaffoldKey.currentState.showSnackBar(new SnackBar(
                        content: new Text("Sample text!"),
                        duration: new Duration(seconds: 5),
                        action: new SnackBarAction(
                          label: "CLICK ME",
                          onPressed: _clickedMe,
                        ),
                      ),);},
                  ),
                ],),
                withLocalStorage: true,
              );

These give errors:
1)

I/flutter ( 4430): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════
I/flutter ( 4430): The following NoSuchMethodError was thrown while handling a gesture:
I/flutter ( 4430): The method 'showSnackBar' was called on null.
I/flutter ( 4430): Receiver: null
I/flutter ( 4430): Tried calling: showSnackBar(Instance of 'SnackBar')
I/flutter ( 4430):

and 2)

I/flutter ( 4430): ══╡ EXCEPTION CAUGHT BY GESTURE ╞═══════════════════════════════════════════════════════════════════
I/flutter ( 4430): The following assertion was thrown while handling a gesture:
I/flutter ( 4430): Scaffold.of() called with a context that does not contain a Scaffold.
I/flutter ( 4430): No Scaffold ancestor could be found starting from the context that was passed to Scaffold.of(). This
I/flutter ( 4430): usually happens when the context provided is from the same StatefulWidget as that whose build
I/flutter ( 4430): function actually creates the Scaffold widget being sought.
I/flutter ( 4430): There are several ways to avoid this problem. The simplest is to use a Builder to get a context that
I/flutter ( 4430): is "under" the Scaffold. For an example of this, please see the documentation for Scaffold.of():
I/flutter ( 4430):   https://docs.flutter.io/flutter/material/Scaffold/of.html
I/flutter ( 4430): A more efficient solution is to split your build function into several widgets. This introduces a
I/flutter ( 4430): new context from which you can obtain the Scaffold. In this solution, you would have an outer widget
I/flutter ( 4430): that creates the Scaffold populated by instances of your new inner widgets, and then in these inner
I/flutter ( 4430): widgets you would use Scaffold.of().
I/flutter ( 4430): A less elegant but more expedient solution is assign a GlobalKey to the Scaffold, then use the
I/flutter ( 4430): key.currentState property to obtain the ScaffoldState rather than using the Scaffold.of() function.
I/flutter ( 4430): The context used was:
I/flutter ( 4430):   Builder
I/flutter ( 4430):
I/flutter ( 4430): When the exception was thrown, this was the stack:
I/flutter ( 4430): #0      Scaffold.of (package:flutter/src/material/scaffold.dart:944:5)

But both do not work. As for AlertDialog it is displayed behind this scaffold. I think that this is because WebviewScaffold extends StatefulWidget instead of Scaffold. Please fix.

[lejard-h]

It won't be possible, the webview is not inside the widget tree, it is on top of the scaffold, so all snackbar or alert dialog will appear under the webview

[MaskyS]

Wouldn't the inability to show snackbars, dialogs etc in a webView still be considered a bug/issue? These elements are supposed to be above almost everything else according to material guidelines: https://material.io/guidelines/components/snackbars-toasts.html#

[lejard-h]

This is technically impossible, the webview is not inside flutter but on top of it.

See this for inline webview, flutter/flutter#730