CameraView issue - EventToCommandBehavior: Couldn't resolve the event

[slprog1]

Hello there,
I'm using CameraView and EventToCommandBehavior to create some sort of a simple app that makes photos.
But I've faced with the issue of using EventToCommandBehavior. When running app in Release mode on both android emulator and real device I do see the following error in Application Output:

[MonoDroid] UNHANDLED EXCEPTION:
[MonoDroid] Android.Runtime.JavaProxyThrowable: Exception of type 'Android.Runtime.JavaProxyThrowable' was thrown.
[MonoDroid] --- End of managed Android.Runtime.JavaProxyThrowable stack trace ---
[MonoDroid] android.runtime.JavaProxyThrowable: System.ArgumentException: EventToCommandBehavior: Couldn't resolve the event.
[MonoDroid] Parameter name: EventName

The code itself isn't that complicated:

<xct:CameraView
               x:Name="CameraView"
               BindingContext="{Binding CameraModel}"
               CameraOptions="{Binding CameraOption}"
               HorizontalOptions="FillAndExpand"
               VerticalOptions="FillAndExpand"
               CaptureMode="Photo">
               <xct:CameraView.Behaviors>
                   <xct:EventToCommandBehavior EventName="MediaCaptured" Command="{Binding CaptureCommand}" />
               </xct:CameraView.Behaviors>
</xct:CameraView>

The Environment is the latest one at this moment:

Visual Studio Community 2019 for Mac
Version 8.10.3 (build 15)
Installation UUID: c4debf69-38dc-430a-b7ff-71b5f73fb9f3
GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 6.18.0.23 (d16-6 / 088c73638)

Package version: 612000140

Mono Framework MDK
Runtime:
Mono 6.12.0.140 (2020-02/51d876a041e) (64-bit)
Package version: 612000140

Roslyn (Language Service)
3.10.0-4.21269.26+029847714208ebe49668667c60ea5b0a294e0fcb

NuGet
Version: 5.9.0.7134

.NET Core SDK
SDK: /usr/local/share/dotnet/sdk/5.0.301/Sdks
SDK Versions:
5.0.301

Thanks in advance for helping!!

[GUOLDEV]

Hi @slprog1, could you please share the Command that you are Binding to? It works for me without any error on Android, but I had to specify the event args as MediaCapturedEventArgs :

public DelegateCommand<MediaCapturedEventArgs> MediaCapturedCommand { get; }

private void ExecuteMediaCapturedCommand(MediaCapturedEventArgs e)
{
...
}

Also, I have created issue report #1442 that maybe is related to the issue that you are experiencing.

[slprog1]

Hi @GUOLDEV , thanks for replying!!
Regarding the command I'm binding to, well it's nothing special here, just a command, which was accepting the object as a parameter type. I did try to specify the exact type MediaCapturedEventArgs as you mentioned, but still the behaviour is the same - in Release mode it does no work(
When adding event handler and doing all needed stuff for me there - it works fine. But that is the thing - I need to "bind" the event to command from my ViewModel :)

[GUOLDEV]

All good 👍 by the way, the code that I posted is in the ViewModel and it works. When I have a chance I will try in release mode as you reported to make sure it works.

[GUOLDEV]

Hi @slprog1 I can reproduce the issue that you reported, CameraView.Behaviors works only in Debug Mode.
I am using code-behind as a workaround for now. Hope it helps.

Workaround

<xct:CameraView
      ...
      MediaCaptured="CameraView_MediaCaptured"/>

private void CameraView_MediaCaptured(object sender, MediaCapturedEventArgs e)
    () => viewModel?.MediaCapturedCommand?.Execute(e);

@jfversluis @pictos @AndreiMisiukevich could you please add a bug label to this issue if you think it is necessary? Thanks in advance.
It can be an issue with EventToCommandBehavior as well, but I have used it with different controls (ListView.Behaviors for example) and never had a problem.

Basic Information
Version with issue: 1.2.0
IDE: Visual Studio
Platform Target Frameworks:
Android: Galaxy S9+ Version 10
iOS: iPhone 11 Version 14.6

[pictos]

@GUOLDEV can you change the Linker configuration in DEBUG mode to be Link SDK and assemblies? After that let me know if the issue happens in Debug as well. Thanks in advance.

[GUOLDEV]

@pictos thanks mate for the prompt reply. I have tested and it stops working setting the Linking to "Sdk Assemblies Only" or "Sdk and User Assemblies" in DEBUG mode. I have tested on Galaxy S9+ Android 10. Please let me know if I can help with any other info.

[pictos]

Yeah, this looks like a linker issue. I'll try to investigate this tomorrow or next week. Thanks for your help ❤

[pictos]

@GUOLDEV if you can attach your repro here will be amazing!

[GUOLDEV]

@pictos do you mean the sample code? If so, you can find it here.

[GUOLDEV]

@pictos do you think it is affecting just CameraView or other controls in general? Sorry, I didn't have time to try other controls to confirm that. If it is just CameraView it would be good to add the CameraView label.

[pictos]

@GUOLDEV I didn't test either, for now, I'll assume that issue is general

[GUOLDEV]

@pictos I have created a PR for the CameraView Linker issue. Could you please have a look when you have a chance? Thanks in advance. I have tested on Android and iOS.

I checked other XCT's Views and it seems the CameraView is the only one having this issue as other views don't have events or the event is used somewhere, so the Linker does not remove it.

Events removed by the Linker:

• MediaCaptured
• MediaCaptureFailed

💡 We already use this approach in XCT, for example in TabView.shared.cs