Improve camera refresh logic during initialization

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

@@ -5,12 +5,11 @@
                 xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
                 xmlns:viewModels="clr-namespace:CommunityToolkit.Maui.Sample.ViewModels.Views"
                 Title="CameraView"
-                Unloaded="OnUnloaded"
                 x:Class="CommunityToolkit.Maui.Sample.Pages.Views.CameraViewPage"
                 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"

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

@@ -1,4 +1,3 @@
-using System.Diagnostics;
 using CommunityToolkit.Maui.Core;
 using CommunityToolkit.Maui.Sample.ViewModels.Views;
 using CommunityToolkit.Maui.Storage;
@@ -9,6 +8,7 @@ public sealed partial class CameraViewPage : BasePage<CameraViewViewModel>
 {
 	readonly IFileSaver fileSaver;
 	readonly string imagePath;
+	bool isInitialized = false;
 
 	int pageCount;
 	Stream videoRecordingStream = Stream.Null;
@@ -21,27 +21,27 @@ public CameraViewPage(CameraViewViewModel viewModel, IFileSystem fileSystem, IFi
 		imagePath = Path.Combine(fileSystem.CacheDirectory, "camera-view-image.jpg");
 
 		Camera.MediaCaptured += OnMediaCaptured;
-
-		Loaded += (s, e) => { pageCount = Navigation.NavigationStack.Count; };
 	}
 
 	protected override async void OnAppearing()
 	{
 		base.OnAppearing();
 
+		if (isInitialized)
+		{
+			return;
+		}
+
 		var cancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(3));
 		await BindingContext.RefreshCamerasCommand.ExecuteAsync(cancellationTokenSource.Token);
+		isInitialized = true;
 	}
 
-	// https://github.com/dotnet/maui/issues/16697
-	// https://github.com/dotnet/maui/issues/15833
 	protected override void OnNavigatedFrom(NavigatedFromEventArgs args)
 	{
 		base.OnNavigatedFrom(args);
 
-		Debug.WriteLine($"< < OnNavigatedFrom {pageCount} {Navigation.NavigationStack.Count}");
-
-		if (Navigation.NavigationStack.Count < pageCount)
+		if (!Shell.Current.Navigation.NavigationStack.Contains(this))
 		{
 			Cleanup();
 		}
@@ -60,12 +60,6 @@ async void OnImageTapped(object? sender, TappedEventArgs args)
 	void Cleanup()
 	{
 		Camera.MediaCaptured -= OnMediaCaptured;
-		Camera.Handler?.DisconnectHandler();
-	}
-
-	void OnUnloaded(object? sender, EventArgs e)
-	{
-		//Cleanup();
 	}
 
 	void OnMediaCaptured(object? sender, MediaCapturedEventArgs e)
@@ -78,7 +72,7 @@ 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

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

@@ -1,6 +1,5 @@
 using System.Runtime.Versioning;
 using Android.Content;
-using Android.Provider;
 using Android.Runtime;
 using Android.Views;
 using AndroidX.Camera.Core;
@@ -48,10 +47,10 @@ public async Task SetExtensionMode(int mode, CancellationToken token)
 	{
 		extensionMode = mode;
 		if (cameraView.SelectedCamera is null
-		    || processCameraProvider is null
-		    || cameraPreview is null
-		    || imageCapture is null
-		    || videoCapture is null)
+			|| processCameraProvider is null
+			|| cameraPreview is null
+			|| imageCapture is null
+			|| videoCapture is null)
 		{
 			return;
 		}
@@ -104,7 +103,7 @@ public async partial ValueTask UpdateCaptureResolution(Size resolution, Cancella
 		if (resolutionFilter is not null)
 		{
 			if (Math.Abs(resolutionFilter.TargetSize.Width - resolution.Width) < double.Epsilon &&
-			    Math.Abs(resolutionFilter.TargetSize.Height - resolution.Height) < double.Epsilon)
+				Math.Abs(resolutionFilter.TargetSize.Height - resolution.Height) < double.Epsilon)
 			{
 				return;
 			}
@@ -164,6 +163,7 @@ protected virtual void Dispose(bool disposing)
 			previewView?.Dispose();
 			previewView = null;
 
+			processCameraProvider?.UnbindAll();
 			processCameraProvider?.Dispose();
 			processCameraProvider = null;
 
@@ -196,16 +196,6 @@ 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();
@@ -258,15 +248,7 @@ protected virtual async partial Task PlatformStartCameraPreview(CancellationToke
 			return;
 		}
 
-		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");
 
 		camera = await RebindCamera(processCameraProvider, cameraView.SelectedCamera, token, cameraPreview, imageCapture, videoCapture);
 		cameraControl = camera.CameraControl;
@@ -306,27 +288,19 @@ protected virtual partial ValueTask PlatformTakePicture(CancellationToken token)
 	protected virtual async partial Task PlatformStartVideoRecording(Stream stream, CancellationToken token)
 	{
 		if (previewView is null
-		    || processCameraProvider is null
-		    || cameraPreview is null
-		    || imageCapture is null
-		    || videoCapture is null
-		    || videoRecorder is null
-		    || videoRecordingFile is not null)
+			|| processCameraProvider is null
+			|| cameraPreview is null
+			|| imageCapture is null
+			|| videoCapture is null
+			|| videoRecorder is null
+			|| videoRecordingFile is not null)
 		{
 			return;
 		}
 
 		videoRecordingStream = stream;
 
-		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");
 
 		if (camera is null || !IsVideoCaptureAlreadyBound())
 		{
@@ -352,9 +326,9 @@ protected virtual async partial Task<Stream> PlatformStopVideoRecording(Cancella
 	{
 		ArgumentNullException.ThrowIfNull(cameraExecutor);
 		if (videoRecording is null
-		    || videoRecordingFile is null
-		    || videoRecordingFinalizeTcs is null
-		    || videoRecordingStream is null)
+			|| videoRecordingFile is null
+			|| videoRecordingFinalizeTcs is null
+			|| videoRecordingStream is null)
 		{
 			return Stream.Null;
 		}
@@ -373,8 +347,8 @@ protected virtual async partial Task<Stream> PlatformStopVideoRecording(Cancella
 	bool IsVideoCaptureAlreadyBound()
 	{
 		return processCameraProvider is not null
-		       && videoCapture is not null
-		       && processCameraProvider.IsBound(videoCapture);
+			   && videoCapture is not null
+			   && processCameraProvider.IsBound(videoCapture);
 	}
 
 	void CleanupVideoRecordingResources()

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

@@ -84,24 +84,18 @@ 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 =>
@@ -123,20 +117,11 @@ 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);
 	}
 
@@ -155,11 +140,7 @@ 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

@@ -15,7 +15,7 @@
 /// <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
@@ -51,7 +51,15 @@
 	/// 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 (cameraProvider.AvailableCameras is null)
+		{
+			await cameraProvider.RefreshAvailableCameras(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 +166,17 @@ 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)
-		{
-			await cameraProvider.RefreshAvailableCameras(token);
-			cameraView.SelectedCamera = cameraProvider.AvailableCameras?.FirstOrDefault() ?? throw new CameraException("No camera available on device");
-		}
-
 		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

@@ -90,7 +90,6 @@ protected override async void ConnectHandler(NativePlatformCameraPreviewView pla
 
 		await CameraManager.ArePermissionsGranted();
 		await CameraManager.ConnectCamera(CancellationToken.None);
-		await cameraProvider.RefreshAvailableCameras(CancellationToken.None);
 	}
 
 	/// <inheritdoc/>

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)
+	internal 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)
+	internal 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();
+	internal partial ValueTask PlatformRefreshAvailableCameras(CancellationToken token) => throw new NotSupportedException();
 }