Fix CameraView crash when switching camera on Windows and other CameraView enhancements

samples/CommunityToolkit.Maui.Sample/Pages/Views/CameraView/CameraViewPage.xaml

@@ -10,7 +10,7 @@
                 x:TypeArguments="viewModels:CameraViewViewModel"
                 x:DataType="viewModels:CameraViewViewModel">
 
-    <Grid RowDefinitions="200,*,Auto,Auto" ColumnDefinitions="3*,*">
+    <Grid RowDefinitions="Auto,*,Auto,Auto" ColumnDefinitions="3*,*">
         <toolkit:CameraView
             x:Name="Camera"
             Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="2" Grid.RowSpan="3"
@@ -36,13 +36,13 @@
             </VerticalStackLayout>
         </Grid>
 
-        <ContentView Grid.Column="1" Grid.Row="0" ZIndex="100" BackgroundColor="#80CCCCCC">
+        <Grid Grid.Column="1" Grid.Row="0" ZIndex="100" BackgroundColor="#80CCCCCC">
             <Image x:Name="image" VerticalOptions="Fill" HorizontalOptions="Fill">
                 <Image.GestureRecognizers>
                     <TapGestureRecognizer Tapped="OnImageTapped" />
                 </Image.GestureRecognizers>
             </Image>
-        </ContentView>
+        </Grid>
 
         <Grid ColumnDefinitions="Auto,*,Auto"  Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="2" ColumnSpacing="10" Margin="10"
               BackgroundColor="#00000000">
@@ -61,6 +61,12 @@
 
             <FlexLayout Margin="5" JustifyContent="SpaceBetween" Wrap="Wrap">
 
+                <Picker 
+                    Title="Cameras" 
+                    ItemsSource="{Binding Cameras}"
+                    ItemDisplayBinding="{Binding Name}" 
+                    SelectedItem="{Binding SelectedCamera}" />
+
                 <Picker 
                     Title="Flash"
                     IsVisible="{Binding Path=SelectedCamera.IsFlashSupported, FallbackValue=false}"

samples/CommunityToolkit.Maui.Sample/Pages/Views/CameraView/CameraViewPage.xaml.cs

@@ -27,8 +27,7 @@ protected override async void OnAppearing()
 	{
 		base.OnAppearing();
 
-		var cancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(3));
-		await BindingContext.RefreshCamerasCommand.ExecuteAsync(cancellationTokenSource.Token);
+		await BindingContext.InitializeAsync();
 	}
 
 	// https://github.com/dotnet/maui/issues/16697
@@ -75,7 +74,7 @@ void OnMediaCaptured(object? sender, MediaCapturedEventArgs e)
 		{
 			// workaround for https://github.com/dotnet/maui/issues/13858
 #if ANDROID
-            image.Source = ImageSource.FromStream(() => File.OpenRead(imagePath));
+			image.Source = ImageSource.FromStream(() => File.OpenRead(imagePath));
 #else
 			image.Source = ImageSource.FromFile(imagePath);
 #endif

samples/CommunityToolkit.Maui.Sample/ViewModels/Views/CameraView/CameraViewViewModel.cs

@@ -1,5 +1,5 @@
-using CommunityToolkit.Maui.Core;
-using CommunityToolkit.Maui.Core.Primitives;
+using System.Collections.ObjectModel;
+using CommunityToolkit.Maui.Core;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 
@@ -9,9 +9,9 @@ public partial class CameraViewViewModel(ICameraProvider cameraProvider) : BaseV
 {
 	readonly ICameraProvider cameraProvider = cameraProvider;
 
-	public IReadOnlyList<CameraInfo> Cameras => cameraProvider.AvailableCameras ?? [];
-
 	public CancellationToken Token => CancellationToken.None;
+
+	public ObservableCollection<CameraInfo> Cameras { get; } = [];
 
 	public ICollection<CameraFlashMode> FlashModes { get; } = Enum.GetValues<CameraFlashMode>();
 
@@ -42,6 +42,18 @@ public partial class CameraViewViewModel(ICameraProvider cameraProvider) : BaseV
 	[ObservableProperty]
 	public partial string ResolutionText { get; set; } = string.Empty;
 
+	public async ValueTask InitializeAsync()
+	{
+		if (!cameraProvider.IsInitialized)
+		{
+			await cameraProvider.InitializeAsync(CancellationToken.None);
+			foreach (var camera in cameraProvider.AvailableCameras ?? [])
+			{
+				Cameras.Add(camera);
+			}
+		}
+	}
+
 	[RelayCommand]
 	async Task RefreshCameras(CancellationToken token) => await cameraProvider.RefreshAvailableCameras(token);
 
@@ -60,6 +72,22 @@ partial void OnSelectedResolutionChanged(Size value)
 		UpdateResolutionText();
 	}
 
+	partial void OnSelectedCameraChanged(CameraInfo? oldValue, CameraInfo? newValue)
+	{
+		UpdateCameraInfoText();
+	}
+
+	void UpdateCameraInfoText()
+	{
+		if (SelectedCamera is null)
+		{
+			return;
+		}
+		CameraNameText = $"{SelectedCamera.Name}";
+		ZoomRangeText = $"Min Zoom: {SelectedCamera.MinimumZoomFactor}, Max Zoom: {SelectedCamera.MaximumZoomFactor}";
+		UpdateFlashModeText();
+	}
+
 	void UpdateFlashModeText()
 	{
 		if (SelectedCamera is null)

src/CommunityToolkit.Maui.Camera/CameraManager.android.cs

@@ -129,6 +129,7 @@ protected virtual void Dispose(bool disposing)
 			previewView?.Dispose();
 			previewView = null;
 
+			processCameraProvider?.UnbindAll();
 			processCameraProvider?.Dispose();
 			processCameraProvider = null;
 
@@ -158,16 +159,6 @@ protected virtual async partial Task PlatformConnectCamera(CancellationToken tok
 		{
 			processCameraProvider = (ProcessCameraProvider)(cameraProviderFuture.Get() ?? throw new CameraException($"Unable to retrieve {nameof(ProcessCameraProvider)}"));
 
-			if (cameraProvider.AvailableCameras is null)
-			{
-				await cameraProvider.RefreshAvailableCameras(token);
-
-				if (cameraProvider.AvailableCameras is null)
-				{
-					throw new CameraException("Unable to refresh available cameras");
-				}
-			}
-
 			await StartUseCase(token);
 
 			cameraProviderTCS.SetResult();
@@ -200,22 +191,14 @@ protected async Task StartUseCase(CancellationToken token)
 		await StartCameraPreview(token);
 	}
 
-	protected virtual async partial Task PlatformStartCameraPreview(CancellationToken token)
+	protected virtual partial Task PlatformStartCameraPreview(CancellationToken token)
 	{
 		if (previewView is null || processCameraProvider is null || cameraPreview is null || imageCapture is null)
 		{
-			return;
+			return Task.CompletedTask;
 		}
 
-		if (cameraView.SelectedCamera is null)
-		{
-			if (cameraProvider.AvailableCameras is null)
-			{
-				await cameraProvider.RefreshAvailableCameras(token);
-			}
-
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
-		}
+		cameraView.SelectedCamera ??= cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
 
 		var cameraSelector = cameraView.SelectedCamera.CameraSelector ?? throw new CameraException($"Unable to retrieve {nameof(CameraSelector)}");
 
@@ -231,6 +214,7 @@ protected virtual async partial Task PlatformStartCameraPreview(CancellationToke
 
 		IsInitialized = true;
 		OnLoaded.Invoke();
+		return Task.CompletedTask;
 	}
 
 	protected virtual partial void PlatformStopCameraPreview()

src/CommunityToolkit.Maui.Camera/CameraManager.macios.cs

@@ -77,24 +77,18 @@ public partial void UpdateZoom(float zoomLevel)
 		captureDevice.UnlockForConfiguration();
 	}
 
-	public async partial ValueTask UpdateCaptureResolution(Size resolution, CancellationToken token)
+	public partial ValueTask UpdateCaptureResolution(Size resolution, CancellationToken token)
 	{
-		if (captureDevice is null)
+		if (captureDevice is null || cameraView.SelectedCamera is null)
 		{
-			return;
+			return ValueTask.CompletedTask;
 		}
 
 		captureDevice.LockForConfiguration(out NSError? error);
 		if (error is not null)
 		{
 			Trace.WriteLine(error);
-			return;
-		}
-
-		if (cameraView.SelectedCamera is null)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
+			return ValueTask.CompletedTask;
 		}
 
 		var filteredFormatList = cameraView.SelectedCamera.SupportedFormats.Where(f =>
@@ -116,20 +110,11 @@ public async partial ValueTask UpdateCaptureResolution(Size resolution, Cancella
 		}
 
 		captureDevice.UnlockForConfiguration();
+		return ValueTask.CompletedTask;
 	}
 
 	protected virtual async partial Task PlatformConnectCamera(CancellationToken token)
 	{
-		if (cameraProvider.AvailableCameras is null)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-
-			if (cameraProvider.AvailableCameras is null)
-			{
-				throw new CameraException("Unable to refresh cameras");
-			}
-		}
-
 		await PlatformStartCameraPreview(token);
 	}
 
@@ -148,11 +133,7 @@ protected virtual async partial Task PlatformStartCameraPreview(CancellationToke
 			input.Dispose();
 		}
 
-		if (cameraView.SelectedCamera is null)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
-		}
+		cameraView.SelectedCamera ??= cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
 
 		captureDevice = cameraView.SelectedCamera.CaptureDevice ?? throw new CameraException($"No Camera found");
 		captureInput = new AVCaptureDeviceInput(captureDevice, out _);

src/CommunityToolkit.Maui.Camera/CameraManager.shared.cs

@@ -13,7 +13,7 @@
 /// <exception cref="NullReferenceException">Thrown when no <see cref="CameraProvider"/> can be resolved.</exception>
 /// <exception cref="InvalidOperationException">Thrown when there are no cameras available.</exception>
 partial class CameraManager(
 	IMauiContext mauiContext,
 	ICameraView cameraView,
 	ICameraProvider cameraProvider,
 	Action onLoaded) : IDisposable
@@ -33,7 +33,18 @@
 	/// Connects to the camera.
 	/// </summary>
 	/// <returns>A <see cref="ValueTask"/> that can be awaited.</returns>
-	public Task ConnectCamera(CancellationToken token) => PlatformConnectCamera(token);
+	public async Task ConnectCamera(CancellationToken token)
+	{
+		if (await ArePermissionsGranted() is false)
+		{
+			throw new PermissionException("Camera permissions not granted");
+		}
+
+		await cameraProvider.InitializeAsync(token);
+		cameraView.SelectedCamera ??= cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
+
+		await PlatformConnectCamera(token);
+	}
 
 	/// <summary>
 	/// Disconnects from the camera.

src/CommunityToolkit.Maui.Camera/CameraManager.windows.cs

@@ -119,16 +119,6 @@ protected virtual void Dispose(bool disposing)
 
 	protected virtual async partial Task PlatformConnectCamera(CancellationToken token)
 	{
-		if (cameraProvider.AvailableCameras is null)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-
-			if (cameraProvider.AvailableCameras is null)
-			{
-				throw new CameraException("Unable to refresh cameras");
-			}
-		}
-
 		await StartCameraPreview(token);
 	}
 
@@ -139,13 +129,9 @@ protected virtual async partial Task PlatformStartCameraPreview(CancellationToke
 			return;
 		}
 
-		mediaCapture = new MediaCapture();
+		cameraView.SelectedCamera ??= cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
 
-		if (cameraView.SelectedCamera is null)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
-		}
+		mediaCapture = new MediaCapture();
 
 		await mediaCapture.InitializeCameraForCameraView(cameraView.SelectedCamera.DeviceId, token);
 
@@ -180,22 +166,22 @@ protected virtual partial void PlatformStopCameraPreview()
 
 	protected async Task PlatformUpdateResolution(Size resolution, CancellationToken token)
 	{
-		if (!IsInitialized || mediaCapture is null)
+		if (!IsInitialized || mediaCapture is null || cameraView.SelectedCamera is null)
 		{
 			return;
 		}
 
-		if (cameraView.SelectedCamera is null)
+		if (mediaCapture.VideoDeviceController.Id != cameraView.SelectedCamera.DeviceId)
 		{
-			await cameraProvider.RefreshAvailableCameras(token);
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
+			return;
 		}
 
 		var filteredPropertiesList = cameraView.SelectedCamera.ImageEncodingProperties.Where(p => p.Width <= resolution.Width && p.Height <= resolution.Height).ToList();
 
-		filteredPropertiesList = filteredPropertiesList.Count is not 0
-			? filteredPropertiesList
-			: [.. cameraView.SelectedCamera.ImageEncodingProperties.OrderByDescending(p => p.Width * p.Height)];
+		if (filteredPropertiesList.Count is 0)
+		{
+			filteredPropertiesList = [.. cameraView.SelectedCamera.ImageEncodingProperties.OrderByDescending(p => p.Width * p.Height)];
+		}
 
 		if (filteredPropertiesList.Count is not 0)
 		{

src/CommunityToolkit.Maui.Camera/Handlers/CameraViewHandler.shared.cs

@@ -87,10 +87,7 @@ void Init(ICameraView view)
 	protected override async void ConnectHandler(NativePlatformCameraPreviewView platformView)
 	{
 		base.ConnectHandler(platformView);
-
-		await CameraManager.ArePermissionsGranted();
 		await CameraManager.ConnectCamera(CancellationToken.None);
-		await cameraProvider.RefreshAvailableCameras(CancellationToken.None);
 	}
 
 	/// <inheritdoc/>

src/CommunityToolkit.Maui.Camera/Interfaces/ICameraProvider.shared.cs

@@ -11,15 +11,30 @@ public interface ICameraProvider
 	/// Cameras available on device
 	/// </summary>
 	/// <remarks>
-	/// List is initialized using <see cref="RefreshAvailableCameras(CancellationToken)"/>
+	/// List is initialized using <see cref="InitializeAsync"/>, and can be refreshed using <see cref="RefreshAvailableCameras(CancellationToken)"/>
 	/// </remarks>
 	IReadOnlyList<CameraInfo>? AvailableCameras { get; }
+
+	/// <summary>
+	/// Gets a value indicating whether the camera provider has been successfully initialized.
+	/// </summary>
+	bool IsInitialized { get; }
 
 	/// <summary>
-	/// Assigns <see cref="AvailableCameras"/> with the cameras available on device
+	/// Refreshes <see cref="AvailableCameras"/> with the cameras available on device.
 	/// </summary>
 	/// <param name="token"></param>
 	/// <returns></returns>
 	[MemberNotNull(nameof(AvailableCameras))]
-	ValueTask RefreshAvailableCameras(CancellationToken token);
+	Task RefreshAvailableCameras(CancellationToken token);
+
+	/// <summary>
+	/// Initialize the camera provider by refreshing the <see cref="AvailableCameras"/>. 
+	/// </summary>
+	/// <remarks>
+	/// If the provider is already initialized, the <see cref="AvailableCameras"/> will not be refreshed again until <see cref="RefreshAvailableCameras(CancellationToken)"/> is called,
+	/// and this method will return a <see cref="ValueTask.CompletedTask"/>.
+	/// </remarks>
+	ValueTask InitializeAsync(CancellationToken token);
+
 }

src/CommunityToolkit.Maui.Camera/Providers/CameraProvider.android.cs

@@ -16,7 +16,7 @@ partial class CameraProvider
 {
 	readonly Context context = Android.App.Application.Context;
 
-	public async partial ValueTask RefreshAvailableCameras(CancellationToken token)
+	private async partial ValueTask PlatformRefreshAvailableCameras(CancellationToken token)
 	{
 		var cameraProviderFuture = ProcessCameraProvider.GetInstance(context);
 

src/CommunityToolkit.Maui.Camera/Providers/CameraProvider.macios.cs

@@ -9,7 +9,7 @@ partial class CameraProvider
 {
 	static readonly AVCaptureDeviceType[] captureDevices = InitializeCaptureDevices();
 
-	public partial ValueTask RefreshAvailableCameras(CancellationToken token)
+	private partial ValueTask PlatformRefreshAvailableCameras(CancellationToken token)
 	{
 		var discoverySession = AVCaptureDeviceDiscoverySession.Create(captureDevices, AVMediaTypes.Video, AVCaptureDevicePosition.Unspecified);
 		var availableCameras = new List<CameraInfo>();

src/CommunityToolkit.Maui.Camera/Providers/CameraProvider.net.cs

@@ -2,5 +2,5 @@ namespace CommunityToolkit.Maui.Core;
 
 partial class CameraProvider
 {
-	public partial ValueTask RefreshAvailableCameras(CancellationToken token) => throw new NotSupportedException();
+	private partial ValueTask PlatformRefreshAvailableCameras(CancellationToken token) => throw new NotSupportedException();
 }