Add ICameraProvider.AvailableCamerasChanged (#2906)

* Add `ICameraProvider.AvailableCamerasChanged`

* Update MockCameraProvider

* Add Unit Tests

* Add Unit Tests

Author: TheCodeTraveler

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

@@ -1,13 +1,19 @@
 using CommunityToolkit.Maui.Core;
-using CommunityToolkit.Maui.Core.Primitives;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 
 namespace CommunityToolkit.Maui.Sample.ViewModels.Views;
 
-public partial class CameraViewViewModel(ICameraProvider cameraProvider) : BaseViewModel
+public partial class CameraViewViewModel : BaseViewModel
 {
-	readonly ICameraProvider cameraProvider = cameraProvider;
+	readonly ICameraProvider cameraProvider;
+
+	public CameraViewViewModel(ICameraProvider cameraProvider)
+	{
+		this.cameraProvider = cameraProvider;
+
+		cameraProvider.AvailableCamerasChanged += HandleAvailableCamerasChanged;
+	}
 
 	public IReadOnlyList<CameraInfo> Cameras => cameraProvider.AvailableCameras ?? [];
 
@@ -78,4 +84,9 @@ void UpdateResolutionText()
 	{
 		ResolutionText = $"Selected Resolution: {SelectedResolution.Width} x {SelectedResolution.Height}";
 	}
+	
+	void HandleAvailableCamerasChanged(object? sender, IReadOnlyList<CameraInfo>? e)
+	{
+		OnPropertyChanged(nameof(Cameras));
+	}
 }

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

@@ -2,6 +2,7 @@
 
 #if IOS || MACCATALYST
 using AVFoundation;
+
 #elif ANDROID
 using AndroidX.Camera.Core;
 #elif WINDOWS
@@ -23,18 +24,18 @@ public class CameraInfo(
 	float maximumZoomFactor,
 	IEnumerable<Size> supportedResolutions
 #if ANDROID
-,
+	,
 	CameraSelector cameraSelector
 #elif IOS || MACCATALYST
-,
+	,
 	AVCaptureDevice captureDevice,
 	IEnumerable<AVCaptureDeviceFormat> supportedFormats
 #elif WINDOWS
-,
+	,
     MediaFrameSourceGroup frameSourceGroup,
 	IEnumerable<ImageEncodingProperties> imageEncodingProperties
 #endif
-)
+) : IEquatable<CameraInfo>
 {
 	/// <summary>
 	/// Gets the name of the camera device.
@@ -82,9 +83,29 @@ IEnumerable<ImageEncodingProperties> imageEncodingProperties
 
 #if WINDOWS
     internal MediaFrameSourceGroup FrameSourceGroup { get; } = frameSourceGroup;
-	internal IReadOnlyList<ImageEncodingProperties> ImageEncodingProperties { get; } =  [.. imageEncodingProperties];
+	internal IReadOnlyList<ImageEncodingProperties> ImageEncodingProperties { get; } = [.. imageEncodingProperties];
 #endif
 
+	/// <inheritdoc cref="Equals(object)"/>
+	/// <remarks>Equality is determined using <see cref="DeviceId"/></remarks>
+	public override bool Equals(object? obj) => Equals(obj as CameraInfo);
+
+	/// <inheritdoc cref="GetHashCode"/>
+	/// <remarks>Uses the <see cref="DeviceId"/></remarks>
+	public override int GetHashCode() => DeviceId.GetHashCode();
+
+	/// <inheritdoc cref="IEquatable{T}.Equals(T)"/>
+	/// <remarks>Equality is determined using <see cref="DeviceId"/></remarks>
+	public bool Equals(CameraInfo? other)
+	{
+		if (other is null)
+		{
+			return false;
+		}
+
+		return DeviceId == other.DeviceId;
+	}
+
 	/// <inheritdoc cref="object.ToString" />
 	public override string ToString()
 	{

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

@@ -7,6 +7,11 @@ namespace CommunityToolkit.Maui.Core;
 /// </summary>
 public interface ICameraProvider
 {
+	/// <summary>
+	/// Event fires when the contents <see cref="AvailableCameras"/> has changed
+	/// </summary>
+	event EventHandler<IReadOnlyList<CameraInfo>?> AvailableCamerasChanged;
+	
 	/// <summary>
 	/// Cameras available on device
 	/// </summary>

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

@@ -5,9 +5,46 @@
 /// </summary>
 partial class CameraProvider : ICameraProvider
 {
+	readonly WeakEventManager availableCamerasChangedEventManager = new();
+	
+	public event EventHandler<IReadOnlyList<CameraInfo>?> AvailableCamerasChanged
+	{
+		add => availableCamerasChangedEventManager.AddEventHandler(value);
+		remove => availableCamerasChangedEventManager.RemoveEventHandler(value);
+	}
+
 	/// <inheritdoc/>
-	public IReadOnlyList<CameraInfo>? AvailableCameras { get; private set; }
+	public IReadOnlyList<CameraInfo>? AvailableCameras
+	{
+		get;
+		private set
+		{
+			if (!AreCameraInfoListsEqual(field, value))
+			{
+				field = value;
+				availableCamerasChangedEventManager.HandleEvent(this, value, nameof(AvailableCamerasChanged));	
+			}
+		}
+	}
 
 	/// <inheritdoc/>
 	public partial ValueTask RefreshAvailableCameras(CancellationToken token);
+
+	internal static bool AreCameraInfoListsEqual(in IReadOnlyList<CameraInfo>? cameraInfoList1, in IReadOnlyList<CameraInfo>? cameraInfoList2)
+	{
+		if (cameraInfoList1 is null && cameraInfoList2 is null)
+		{
+			return true;
+		}
+
+		if (cameraInfoList1 is null || cameraInfoList2 is null)
+		{
+			return false;
+		}
+
+		var cameraInfosInList1ButNotInList2 = cameraInfoList1.Except(cameraInfoList2).ToList();
+		var cameraInfosInList2ButNotInList1 = cameraInfoList2.Except(cameraInfoList1).ToList();
+
+		return cameraInfosInList1ButNotInList2.Count is 0 && cameraInfosInList2ButNotInList1.Count is 0;
+	}
 }

src/CommunityToolkit.Maui.UnitTests/Mocks/MockCameraProvider.cs

@@ -5,7 +5,20 @@ namespace CommunityToolkit.Maui.UnitTests.Mocks;
 
 public class MockCameraProvider : ICameraProvider
 {
-	public IReadOnlyList<CameraInfo>? AvailableCameras { get; private set; }
+	public event EventHandler<IReadOnlyList<CameraInfo>?>? AvailableCamerasChanged;
+
+	public IReadOnlyList<CameraInfo>? AvailableCameras
+	{
+		get;
+		private set
+		{
+			if (!CameraProvider.AreCameraInfoListsEqual(field, value))
+			{
+				field = value;
+				AvailableCamerasChanged?.Invoke(this, value);
+			}
+		}
+	}
 
 	public ValueTask RefreshAvailableCameras(CancellationToken token)
 	{