useLocalContext property
If false (the default), the dialog will appear in the context of the
NavigateAction.navigatorKey. If you don't set up that key, or if you
pass true here, it will use the local context of the
UserExceptionDialog widget.
Make sure this is false if you are putting the UserExceptionDialog in
the builder parameter of the MaterialApp widget, because in this case
the UserExceptionDialog will be above the app's Navigator, and if
you open the dialog in the local context you won't be able to use the
Android back-button to close it.
Implementation
final bool useLocalContext;