XamarinCommunityToolkit: [Bug] [CameraView] [iOS] Taking photos doesn't work on iOS using Hot Restart

Description

I’m using Hot Restart in Windows to debug my Xamarin.Forms app on iOS. Whenever I take a photo (trigger the ShutterCommand), the app UI freezes and the MediaCaptured event never gets called.

I also get this lovely exception:

=================================================================
	Basic Fault Address Reporting
=================================================================
Memory around native instruction pointer (0x1010ae8c4):0x1010ae8b4  a8 83 5e f8 09 00 80 52 09 01 00 39 a8 03 5f f8  ..^....R...9.._.
0x1010ae8c4  09 01 40 39 69 0f 00 34 a8 03 5f f8 09 01 c0 39  ..@9
.

=================================================================
	Managed Stacktrace:
=================================================================

.4.._....9
0x1010ae8d4  29 8d 00 71 e8 03 09 aa 08 7d 40 d3 1f 69 01 f1  )..q.....}@..i..
0x1010ae8e4  e8 13 00 f9 68 0b 00 54 08 00 00 90 08 61 2c 91  ....h..T.....a,
	  at <unknown> <0xffffffff>
	  at UIKit.UIApplication:UIApplicationMain <0x000b8>
	  at UIKit.UIApplication:Main <0x00020>
	  at UIKit.UIApplication:Main <0x00038>
	  at XctCameraApp01.iOS.Application:Main <0x00012>
	  at <Module>:runtime_invoke_direct_void_string[] <0x0008c>
	  at <unknown> <0xffffffff>
	  at System.Reflection.RuntimeMethodInfo:InternalInvoke <0x00030>
	  at System.Reflection.RuntimeMethodInfo:Invoke <0x000fc>
	  at System.Reflection.MethodBase:Invoke <0x0001a>
	  at Xamarin.PreBuilt.iOS.Applications:Main <0x00254>
	  at <Module>:runtime_invoke_direct_void_string[] <0x00092>
=================================================================

Steps to Reproduce

1. CameraPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
    x:Class="XctCameraApp01.MainPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:xct="http://xamarin.com/schemas/2020/toolkit">

    <Grid>
        <xct:CameraView
            x:Name="cameraView"
            CaptureMode="Photo"
            OnAvailable="cameraView_OnAvailable">
            <xct:CameraView.Behaviors>
                <xct:EventToCommandBehavior Command="{Binding PhotoCapturedCommand}" EventName="MediaCaptured" />
            </xct:CameraView.Behaviors>
        </xct:CameraView>
        <Button
            Margin="20"
            Command="{Binding ShutterCommand, Source={x:Reference cameraView}}"
            HorizontalOptions="Center"
            IsEnabled="{Binding CanTakePhoto}"
            Text="Take photo"
            VerticalOptions="End" />
    </Grid>

</ContentPage>

1. CameraPage.xaml.cs

using Xamarin.Forms;

namespace XctCameraApp01
{
    public partial class MainPage : ContentPage
    {
        private readonly MainViewModel _model;

        public MainPage()
        {
            InitializeComponent();
            BindingContext = _model = new MainViewModel();
        }

        private void cameraView_OnAvailable(object sender, bool e)
        {
            _model.CanTakePhoto = e;
        }
    }
}

1. MainViewModel.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Input;
using Xamarin.CommunityToolkit.ObjectModel;
using Xamarin.CommunityToolkit.UI.Views;
using Xamarin.Essentials;
using Xamarin.Forms;
using static Xamarin.Essentials.Permissions;

namespace XctCameraApp01
{
    public class MainViewModel : ObservableObject
    {
        private bool _canTakePhoto;
        public bool CanTakePhoto
        {
            get => _canTakePhoto;
            set => SetProperty(ref _canTakePhoto, value);
        }

        public ICommand PhotoCapturedCommand => new AsyncCommand<MediaCapturedEventArgs>(PhotoCapturedAsync);

        private async Task PhotoCapturedAsync(MediaCapturedEventArgs args)
        {
            await SavePhotoAsync(args.ImageData);
        }

        private async Task SavePhotoAsync(byte[] photoData)
        {
            var readStatus = await CheckAndRequestPermissionAsync(new StorageRead());
            if (readStatus != PermissionStatus.Granted)
            {
                // Notify user permission was denied
                return;
            }

            var writeStatus = await CheckAndRequestPermissionAsync(new StorageWrite());
            if (writeStatus != PermissionStatus.Granted)
            {
                // Notify user permission was denied
                return;
            }

            var savedPhotoPath = await SavePhotoFileAsync(photoData, Guid.NewGuid().ToString() + ".jpg");

            LastSavedPhotoPath = savedPhotoPath;
        }

        private async Task<string> SavePhotoFileAsync(byte[] photoData, string fileName)
        {
            var dirPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
            Directory.CreateDirectory(dirPath);

            var savedPhotoPath = Path.Combine(dirPath, fileName);

            using (var fs = new FileStream(savedPhotoPath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
            {
                await fs.WriteAsync(photoData, 0, photoData.Length);
                return savedPhotoPath;
            }
        }

        public async Task<PermissionStatus> CheckAndRequestPermissionAsync<T>(T permission) where T : BasePermission
        {
            var status = await permission.CheckStatusAsync();
            if (status != PermissionStatus.Granted)
            {
                status = await permission.RequestAsync();
            }

            return status;
        }
    }
}

1. Launch app on an iOS device using Hot Restart and click the ‘Take photo’ button

Expected Behavior

CameraView takes a photo and triggers the MediaCaptured event

Actual Behavior

The MediaCaptured event doesn’t get triggered, the camera preview keeps going.

Basic Information

• Version with issue: 1.0.2
• Last known good version: ?
• IDE: VS 2019 Professional v16.8.5
• Platform Target Frameworks:
  • iOS: Default (14.3 I guess)
  • Android: 10.0
  • UWP: nope
• Android Support Library Version: Android X
• Nuget Packages:
  • Xamarin.Forms 5.0.0.1931
  • Xamarin.Essentials 1.6.1
• Affected Devices:
  • iPad Air 2 (iOS 13.7)

Reproduction repo

https://github.com/michaldivis/camera-view-app