Exception if swipe to dismiss modal page on iOS (Simulator, real device not tested yet)

[AndreasReitberger]

Description

If a modal page gets dismissed with the swipe down gesture, a crash occurs on iOS.

Object reference not set to an instance of an object. (System.NullReferenceException)
at Microsoft.Maui.Controls.Platform.ModalWrapper.DidDismiss(UIPresentationController presentationController)
at System.Threading.Tasks.Task.<>c.b__128_0(Object state)
at Foundation.NSAsyncSynchronizationContextDispatcher.Apply()

StackTrace

Objective-C exception thrown. Name: System.NullReferenceException Reason: Object reference not set to an instance of an object. (System.NullReferenceException)
at Microsoft.Maui.Controls.Platform.ModalWrapper.DidDismiss(UIPresentationController presentationController)
at System.Threading.Tasks.Task.<>c.b__128_0(Object state)
at Foundation.NSAsyncSynchronizationContextDispatcher.Apply()

Native stack trace:
0 CoreFoundation 0x000000010fcbcd44 __exceptionPreprocess + 242
1 libobjc.A.dylib 0x000000011cb6fa65 objc_exception_throw + 48
2 libxamarin-dotnet-debug.dylib 0x000000010b7391ef xamarin_process_managed_exception + 943
3 KlipperRemoteControl 0x0000000102712de9 _ZL31native_to_managed_trampoline_10P11objc_objectP13objc_selectorPP11_MonoMethodj + 361
4 KlipperRemoteControl 0x00000001027135c9 -[__MonoMac_NSAsyncSynchronizationContextDispatcher xamarinApplySelector] + 41
5 Foundation 0x0000000112ca53bf __NSThreadPerformPerform + 179
6 CoreFoundation 0x000000010fc29833 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 17
7 CoreFoundation 0x000000010fc2972b __CFRunLoopDoSource0 + 180
8 CoreFoundation 0x000000010fc28bf8 __CFRunLoopDoSources0 + 242
9 CoreFoundation 0x000000010fc232f4 __CFRunLoopRun + 871
10 CoreFoundation 0x000000010fc22a90 CFRunLoopRunSpecific + 562
11 GraphicsServices 0x000000011f8bdc8e GSEventRunModal + 139
12 UIKitCore 0x000000012823690e -[UIApplication _run] + 928
13 UIKitCore 0x000000012823b569 UIApplicationMain + 101
14 libmonosgen-2.0.dylib 0x000000010bf26b52 do_icall + 194
15 libmonosgen-2.0.dylib 0x000000010bf25b6d do_icall_wrapper + 253
16 libmonosgen-2.0.dylib 0x000000010bf17d8a interp_exec_method + 2970
17 libmonosgen-2.0.dylib 0x000000010bf1600f interp_runtime_invoke + 239
18 libmonosgen-2.0.dylib 0x000000010be0dcfb mono_jit_runtime_invoke + 1227
19 libmonosgen-2.0.dylib 0x000000010bd30498 mono_runtime_invoke_checked + 136
20 libmonosgen-2.0.dylib 0x000000010bd3723b mono_runtime_exec_main_checked + 107
21 libmonosgen-2.0.dylib 0x000000010be70192 mono_jit_exec + 354
22 libxamarin-dotnet-debug.dylib 0x000000010b74d0ad xamarin_main + 1949
23 KlipperRemoteControl 0x00000001027a4964 main + 52
24 dyld 0x000000010b320f21 start_sim + 10
25 ??? 0x0000000202cc251e 0x0 + 8636867870
26 ??? 0x0000000000000003 0x0 + 3

Style for the modal page => ModalPageStyle

<?xml version="1.0" encoding="utf-8" ?>
<?xaml-comp compile="true" ?>
<ResourceDictionary
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    
    xmlns:ios="clr-namespace:Microsoft.Maui.Controls.PlatformConfiguration.iOSSpecific;assembly=Microsoft.Maui.Controls"
    >
    <Style TargetType="Page" ApplyToDerivedTypes="True">
        <Setter Property="Padding" Value="0"/>
        <Setter Property="BackgroundColor" Value="{AppThemeBinding Light={DynamicResource White}, Dark={DynamicResource Black}}" />
    </Style>

    <Style TargetType="NavigationPage">
        <Setter Property="BarBackgroundColor" Value="{AppThemeBinding Light={DynamicResource White}, Dark={DynamicResource Black}}" />
        <Setter Property="BarTextColor" Value="{AppThemeBinding Light={DynamicResource PrimaryColor}, Dark={DynamicResource White}}" />
        <Setter Property="IconColor" Value="{AppThemeBinding Light={DynamicResource PrimaryColor}, Dark={DynamicResource White}}" />
    </Style>

    <Style TargetType="TabbedPage">
        <Setter Property="BarBackgroundColor" Value="{AppThemeBinding Light={DynamicResource White}, Dark={DynamicResource Black}}" />
        <Setter Property="BarTextColor" Value="{AppThemeBinding Light={DynamicResource PrimaryColor}, Dark={DynamicResource White}}" />
        <Setter Property="UnselectedTabColor" Value="{AppThemeBinding Light={DynamicResource LightGray}, Dark={DynamicResource DarkGray}}" />
        <Setter Property="SelectedTabColor" Value="{AppThemeBinding Light={DynamicResource DarkGray}, Dark={DynamicResource LightGray}}" />
    </Style>

    <Style x:Key="DefaultPageStyle" TargetType="ContentPage">
        <Setter Property="BackgroundColor" Value="{AppThemeBinding Light={DynamicResource White}, Dark={DynamicResource Black}}" />
    </Style>

    <Style x:Key="ModalPageStyle" TargetType="ContentPage" BasedOn="{StaticResource DefaultPageStyle}">
        <Setter Property="Shell.PresentationMode" Value="ModalAnimated" />
        <Setter Property="ios:Page.ModalPresentationStyle" Value="{OnIdiom Tablet=Automatic, Default=FormSheet}" />
    </Style>
</ResourceDictionary>

Steps to Reproduce

1. Apply the style to a ContentPage
2. Open the page with the ShellNavigationManger (Shell.Current.GoTo....)
3. Swipe down to dismiss

Version with bug

Release Candidate 2 (current)

Last version that worked well

Unknown/Other

Affected platforms

iOS, I was not able test on other platforms

Affected platform versions

iOS 15.4

Did you find any workaround?

This bug was already in Xamarin.Forms, but it was fixed a few releases ago in Xamarin.Forms.
Maybe this helps.

Relevant log output

No response

[jfversluis]

@AndreasReitberger do you happen to have a link to the Xamarin.Forms one?

Probably this one: xamarin/Xamarin.Forms#14527

Checking what happened now...

[AndreasReitberger]

@jfversluis
xamarin/Xamarin.Forms#12300
xamarin/Xamarin.Forms#14295 (different issue, but also related to modal pages on iOS)

Thanks for looking into this!

[jfversluis]

Is that 14295 also fixed for Forms or is that one still open?

I tried to apply the fix I did for Forms on this one, but seems that doesn't work. So this bug might be slightly different unfortunately.

[AndreasReitberger]

In Xamarin.Forms it's still a bug. But I haven't tried it in MAUI yet, because at the moment the app crashes afterwards closing the modal.
Once this is fixed, I'll try it and open a new issue if needed.

Best,
Andreas