Xamarin.Forms Shell lifecycle
Shell applications respect the Xamarin.Forms lifecycle, and additionally fire an Appearing event when a page is about to appear on the screen, and a Disappearing event when a page is about to disappear from the screen. These events are propagated to pages, and can be handled by overriding the OnAppearing or OnDisappearing methods on the page.
Note
In a Shell application, the Appearing and Disappearing events are raised from cross-platform code, prior to platform code making a page visible, or removing a page from the screen.
For more information about the Xamarin.Forms app lifecycle, see Xamarin.Forms app lifecycle.
Hierarchical navigation
In a Shell application, pushing a page onto the navigation stack will result in the currently visible ShellContent object, and its page content, raising the Disappearing event. Similarly, popping the last page from the navigation stack will result in the newly visible ShellContent object, and its page content, raising the Appearing event.
For more information about hierarchical navigation, see Xamarin.Forms hierarchical navigation.
Modal navigation
In a Shell application, pushing a modal page onto the modal navigation stack will result in all visible Shell objects raising the Disappearing event. Similarly, popping the last modal page from the modal navigation stack will result in all visible Shell objects raising the Appearing event.
For more information about modal navigation, see Xamarin.Forms modal pages.