App.Current.PageDisappearing is not raised when a page is popped from the navigation stack.

[Keflon]

Description

App.Current.PageDisappearing is not raised when a page is popped from the navigation stack.

Steps to Reproduce

1. Create a File->New MAUI app.
2. Replace the constructor in App.xaml.cs with this:

public partial class App : Application
{
	public App()
	{
		InitializeComponent();
		//MainPage = new AppShell();
		MainPage = new NavigationPage(new MainPage());

        App.Current.PageAppearing += Current_PageAppearing;
        App.Current.PageDisappearing += Current_PageDisappearing;
	}

    private void Current_PageDisappearing(object sender, Page e)
    {
        Debug.WriteLine($"Current_PageDisappearing {e}");
    }

    private void Current_PageAppearing(object sender, Page e)
    {
        Debug.WriteLine($"Current_PageAppearing {e}");
    }
}

3. Replace the click-handler in MainPage.xaml.cs with this:

    private void OnCounterClicked(object sender, EventArgs e)
    {
        App.Current.MainPage.Navigation.PushAsync(new ContentPage { Title="Child Page"});
    }

4. Run the app.
5. Look at the debug output from the new Current_PageDisappearing and Current_PageAppearing event handlers.
6. Observe that MainPage and NavigationPage are reported as appearing.

[0:] Current_PageAppearing MauiPopNavigationBug.MainPage
[0:] Current_PageAppearing Microsoft.Maui.Controls.NavigationPage

8. Tap the button.
9. Observe MainPage disappears and ContentPage appears.

[0:] Current_PageDisappearing MauiPopNavigationBug.MainPage
[0:] Current_PageAppearing Microsoft.Maui.Controls.ContentPage

10. Tap the back button
11. [BUG] Observe the ContentPage is popped, the MainPage appearing event is raised but the ContentPage PageDisappearing event is not raised.

[0:] Current_PageAppearing MauiPopNavigationBug.MainPage

Link to public reproduction project repository

https://github.com/Keflon/MauiPopNavigationBug

Version with bug

7.0 (current)

Last version that worked well

Unknown/Other

Affected platforms

iOS, Android, Windows, I was not able test on other platforms

Affected platform versions

All current / latest.

Did you find any workaround?

Subscribe to the following events:

App.Current.DescendantAdded += CurrentApplication_DescendantAdded;
App.Current.DescendantRemoved += CurrentApplication_DescendantRemoved;

Do something like this:

private void CurrentApplication_DescendantAdded(object sender, ElementEventArgs e)
{
    if (e.Element is Page cp)
    {
        cp.Disappearing += PageDisappearing;
        cp.Appearing += PageAppearing;
    }
}

private async void CurrentApplication_DescendantRemoved(object sender, ElementEventArgs e)
{
    if (e.Element is Page cp)
    {
        cp.Appearing -= PageAppearing;

        await Task.Yield();     // Reason: The disappearing event was/is raised after the DescendantRemoved event.
        cp.Disappearing -= PageDisappearing;
    }
}

The PageAppearing and PageDisappearing events are correctly raised.

The above is not tested, however it is a subset of working CurrentApplication_DescendantAdded and CurrentApplication_DescendantRemoved implementations found here: https://github.com/Keflon/Maui.MvvmZero/blob/eada8a7059fadc248de13456b3be627373384bd8/Maui.MvvmZero/Implementation/PageServiceZero.cs

Relevant log output

[0:] Current_PageAppearing MauiPopNavigationBug.*
[0:] Current_PageDisappearing MauiPopNavigationBug.*

[drasticactions]

Can you try this on Xamarin.Forms and report what it does? Is this a regression from it or does it do the same thing?

[Keflon]

Xamarin.Forms is fine for UWP, iOS and Android.
Repo here: https://github.com/Keflon/XamarinPopNavigationTest/tree/master
I tested Debug builds only.

[rachelkang]

@PureWeen does this issue look familiar / in the domain of what you've been working on recently?

[ghost]

We've added this issue to our backlog, and we will work to address it as time and resources allow. If you have any additional information or questions about this issue, please leave a comment. For additional info about issue management, please read our Triage Process.

[Zhanglirong-Winnie]

Verified this issue with Visual Studio Enterprise 17.7.0 Preview 1.0. Can repro on windows platform with sample project.
MauiPop.zip