Update PopupExtensions.shared.cs

[cat0363]

When I try to show the Popup by calling the PopupShow method inside the NavigatedTo event, it doesn't show up.
Same if I try to show the Popup in the OnAppearing event. I was getting the below exception message.

Could not locate MauiContext.

The location where the exception occurred is the code below called in the CreatePopup method of PopupExtensions.shared.cs.

var mauiContext = GetMauiContext(page);

The Get MauiContext method was implemented like this:

return page.Handler?.MauiContext ?? throw new InvalidOperationException("Could not locate MauiContext.");

The page's Handler is null during the OnAppearing and OnNavigatedTo event timings.
Therefore, MauiContext cannot be obtained. The timing that the Handler of the page can
acquire is the Loaded event.

The implementation before the fix calls CreateAndShowPopup method in the NavigatedTo event.

When the Popup is displayed in the OnAppearing event, the Handler of the page is null, so the exception above is raised.

When the Popup is displayed in the OnNavigatedTo event, the CreateAndShowPopup method is not called because the registration for the NavigatedTo event is performed within the Page's OnNavigatedTo event.

So I changed the CreateAndShowPopup method to be called in the Loaded event instead of the NavigatedTo event.
The Loaded event is a later event than the OnAppearing and OnNavigatedTo events, and the page's Handler is never null.

Description of Change

Linked Issues

• Fixes [BUG] Popup not showing in NavigatedTo event on Shell. #1120

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pull/XYZ

Additional information

page.IsPlatformEnabled is True only in the Loaded event. OnAppearing event, OnNavigatedTo event,
page.IsPlatformEnabled is False. In the OnLoaded event the CreateAndShowPopup method is called
directly, but in the OnAppearing and OnNavigatedTo events it is called within the Loaded event.

Below is the execution result.

[Show the popup inside the OnAppearing event on Android]

Android.Emulator.-.pixel_2_-_api_30_5554.2023-06-09.12-02-19.mp4

[Show the popup inside the OnNavigatedTo event on Android]

Android.Emulator.-.pixel_2_-_api_30_5554.2023-06-09.12-03-45.mp4

[Show the popup inside the Loaded event on Android]

Android.Emulator.-.pixel_2_-_api_30_5554.2023-06-09.12-05-32.mp4

[Show the popup inside the OnAppearing event on iOS]

A_RPReplay_Final1686281776.MP4

[Show the popup inside the OnNavigatedTo event on iOS]

N_RPReplay_Final1686281148.MP4

[Show the popup inside the Loaded event on iOS]

L_RPReplay_Final1686280764.MP4

[cat0363]

@dotnet-policy-service agree

[bijington]

Just adding my approval to say thanks for this effort!