Android Java.Lang.NullPointerException crash in CarouselViewRenderer.SetNativeView when Context is AndroidX.AppCompat.View.ContextThemeWrapper

[vitalii-smal]

First of all, thank you for migrating CarouselView to MAUI!

We faced with a crash, when using regular navigation in the .NET MAUI App project, e.g:
MainPage = new NavigationPage(new MainPage()); (imagine MainPage contains CarouselView)

Java.Lang.NullPointerException crash happens in CarouselViewRenderer.SetNativeView on Android.

It happens because context is StackNavigationManager_StackContext which derives from AndroidX.AppCompat.View.ContextThemeWrapper but CarouselViewRenderer.FindActivity method expects Android.Views.ContextThemeWrapper. So, FindActivity returns null and NullPointerException occurs in CarouselViewRenderer.SetNativeView method.

You can reproduce this issue on the sample project attached.
NullPointerCrashDemo.zip

A FIX is to use Android.Content.ContextWrapper class which contains BaseContext we are looking for and is base class for both AndroidX.AppCompat.View.ContextThemeWrapper and Android.Views.ContextThemeWrapper.

I will create a fork with fix to speed up fix of this issue.

Will appreciate if you can handle it as soon as possible.

Regards,
Vitalii

[orwo1]

Hi @microspaze ,
Any update?

[AlonRom]

@microspaze hi, any updates on this? we must have this fix to the migration.

[microspaze]

PR from @vitalii-smal has been merged. New version of CarouselView.Maui lib has been published to NUGET. https://www.nuget.org/packages/CarouselView.Maui/1.0.7

Thanks very much!

[microspaze]

@vitalii-smal BTW you should not use View array as CarouselViewControl's ItemsSource. Because the View may be disposed when you swip to next carousel view and then swip back. The demo code you provide in NullPointerCrashDemo.zip looks like bellow:

    <cv:CarouselViewControl>
        <cv:CarouselViewControl.ItemsSource>
            <x:Array Type="{x:Type View}">
                <Label Text="1" />
                <Label Text="2" />
                <Label Text="3" />
            </x:Array>
        </cv:CarouselViewControl.ItemsSource>
    </cv:CarouselViewControl>

SHOULD BE CHANGED TO:

    <cv:CarouselViewControl InfiniteScrolling="True">
        <cv:CarouselViewControl.ItemsSource>
            <x:Array Type="{x:Type x:String}">
                <x:String>1</x:String>
                <x:String>2</x:String>
                <x:String>3</x:String>
            </x:Array>
        </cv:CarouselViewControl.ItemsSource>
        <cv:CarouselViewControl.ItemTemplate>
            <DataTemplate>
                <Label Text="{Binding .}" />
            </DataTemplate>
        </cv:CarouselViewControl.ItemTemplate>
    </cv:CarouselViewControl>

[vitalii-smal]

@vitalii-smal BTW you should not use View array as CarouselViewControl's ItemsSource. Because the View may be disposed when you swip to next carousel view and then swip back. The demo code you provide in NullPointerCrashDemo.zip looks like bellow:

    <cv:CarouselViewControl>
        <cv:CarouselViewControl.ItemsSource>
            <x:Array Type="{x:Type View}">
                <Label Text="1" />
                <Label Text="2" />
                <Label Text="3" />
            </x:Array>
        </cv:CarouselViewControl.ItemsSource>
    </cv:CarouselViewControl>

SHOULD BE CHANGED TO:

    <cv:CarouselViewControl InfiniteScrolling="True">
        <cv:CarouselViewControl.ItemsSource>
            <x:Array Type="{x:Type x:String}">
                <x:String>1</x:String>
                <x:String>2</x:String>
                <x:String>3</x:String>
            </x:Array>
        </cv:CarouselViewControl.ItemsSource>
        <cv:CarouselViewControl.ItemTemplate>
            <DataTemplate>
                <Label Text="{Binding .}" />
            </DataTemplate>
        </cv:CarouselViewControl.ItemTemplate>
    </cv:CarouselViewControl>

Thank you! I will check it on MAUI, we used array of Views in Xamarin.Forms version, there were no issues with disposing.

[microspaze]

@vitalii-smal Fixed Android Cannot Access A Disposed Object when use view list as ItemsSource in latest version 1.0.8 https://www.nuget.org/packages/CarouselView.Maui/1.0.8