[Bug] After PopModalAsync will not call OnAppearing (iOS)

[oleksandrtretiak]

Description

Steps to Reproduce

1. Open Page1
2. Push modal Page2
3. PopModalAsync

Expected Behavior

Page1 Call OnAppearing

Actual Behavior

Nothing

Basic Information

• Version with issue: 5 pre6 ~
• Last known good version: 4.8.1451
• Platform Target Frameworks:
  • iOS: iOS, 14.3
• NuGet Packages:
• Affected Devices:

Environment

Screenshots

Reproduction Link

Workaround

[rachelkang]

Hi, @oleksandrtretiak - thanks for submitting this issue! I tried reproducing what you described, but unfortunately wasn't able to. I see the calls to OnAppearing made on both the first page and modal page when running on 5.0pre6. Would you mind sharing your project / a sample project or modifying this sample project to reproduce the behavior you're experiencing? Thanks :)

[oleksandrtretiak]

Hi, @rachelkang ! Sorry that I gave you not enough details.
Use Navigation.PushModalAsync(new NavigationPage(new ModalPage())
{
BackgroundColor = Color.Red
});

The problem with BackgroundColor of NavigationPage;

Or download the updated project.

[beeradmoore]

Came to report the same issue, did not realise the issue is setting BackgroundColor. I'll go try fix that as a workaround for me.

As for this issue, I was able to replicate the issue by changing the Push_Modal method from the original sample to look like so

		void Push_Modal(object sender, EventArgs e)
		{
			Navigation.PushModalAsync(new ModalPage()
			{
				BackgroundColor = Color.Red
			});
		}

Main difference from @oleksandrtretiak comment above is that you don't need to use NavigationPage in the PushModal.

I have updated the sample with a few changes.

• Updated to Xamarin.Forms 5.0.0.1874
• Added comments into MainPage.xaml.cs and ModalPage.xaml.cs to show what to comment in/out to make the events break
• Stopped breakpointing and used System.Diagnostics.Debug.WriteLine to show output instead
• Added OnDissapearing events to show they are not firing as well.
• Changed Android SDK down to Android 10 (from Android 11, as I don't have SDK 30 installed) to confirm its still only an iOS issue.

Issue13258 - beeradmoore.zip

EDIT 1:

Looking into the XF source code ViewDidAppear, ViewWillAppear, ViewDidDisappear in Xamarin.Forms.Platform.iOS.NavigationRenderer do not get called if we called PushModal with new page with the BackgroundColor property set.

I have made a repo issue in the XF control gallery on my own fork here.

EDIT 2:
Using Background instead of BackgroundColor will not produce the same issue. This may be a workaround for some, but I still can't see the underlying issue. In all my years of using Xamarin.iOS I don't believe I've come across a situation where ViewDidAppear would not fire, however there are plenty of results on google of people having the same issue even when not using Xamarin.