I added a logout button to the FlyoutFooter of the shell. After clicking it, it takes a certain waiting time to connect to the server, so I need to add an ActivityIndicator in the flyout.
<Shell.FlyoutFooter>
<Grid>
<Button Text="Logout"
Clicked="Button_Clicked"/>
</Grid>
</Shell.FlyoutFooter>
How can I add it there?

