[Android] OnAppearing only called on 1st tab of AppShell home page

[davefxy]

Description

On the Android, when I have 2 tabs defined for an AppShell homepage, the OnAppearing method doesn't get called for the ContentPage when I select the 2nd tab. It does get called on the 1st tab contentpage which is initially called when the home page is displayed .
I am using Microsoft Visual Studio Community 2022 (64-bit) - Preview
Version 17.4.0 Preview 1.0 on Windows 11.

Steps to Reproduce

1. Compile the attached app for an Android tablet.
2. Place a breakpoint at line 14 (OnAppearing) in DogsPage.xaml.cs
3. Run the app on an Android device(i.e. Samaung Galaxy S7, Android 12, API 31)
4. Select the Dogs tab. It will not break at the OnAppearing method in DogPage.xaml.cs

Version with bug

6.0.312

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 12, API 31

Did you find any workaround?

No

Attached app

Xaminals.zip

No response

[tom-b-iodigital]

I'm having the same problem in one of our projects

[davefxy]

This is a relatively important issue when the page is dependent on OnAppearing() to load the data for the page. Is there another alternative to OnAppearing to accomplish loading the data for the page? Should I attempt to load the data for all of the tabbed pages when the 1st tab page is initialized? Is anyone looking/working on this?

[davefxy]

I think this is already being looked at. Check out "OnAppearing not triggered when going back from Modal page #8513"

[holecekp]

I have also problems with OnAppearing for tabs. It is executed many times on Windows (#10161) and it is not executed at all when tabs are switched on Androind.

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[holecekp]

It is sad that it will not be fixed in the near future. The issue is quite important because it OnAppearing is used to load data (or do other initializations that requires async/await). I am also using OnAppearing/OnDisappearing to subscribe/unsubscribe events, start/stop sound and other task that are done in background. This can cause big problems when these methods does not run when the developer expects them (in case of Android), or if the run multiple times instead of once (in case of Windows).
This also makes the migration of an existing app from Xamarin.Forms to MAUI much more difficult, because the behavior of the app can change completely.

[skynetbeta23]

Having the same issue. Lost two days of work because I thought I was doing some mistakes. MAUI really is full of bugs, and I can accept it because of its juvenility. But bugs like these I think should be prioritized. I must abandon the Tab structure in my app structure because of this issue

[durandt]

This issue has been around for 4 years, already existed in Xamarin.Forms:
xamarin/Xamarin.Forms#3855

This makes AppShell tabs behavior very inconsistent between iOS and Android and is likely to confuse new MAUI developers a lot.
Fixing this should be high prio, considering for how long this issue has been around.

Workaround:
You should be able to listen to the AppShell event when a tab is changed and call your initialization-code there instead.