Fix camera view regression

[zhitaop]

Description of Change

Root cause

The PR #2909 introduced a few regressions that will cause the camera view to throw uncaught exceptions:

• When the camera view is initializing, UpdateCaptureResolution() is called in the CameraViewHandler constructor with the following call stack: CameraViewHandler.PropertyMapper
  =>CameraViewHandler.MapImageCaptureResolution
  => CameraManager.UpdateCaptureResolution()

At this time, cameraView.SelectedCamera is still null, as CameraViewHandler.ConnectHandler() => CameraManager.ConnectCamera has not been called yet. This causes the app to throw an CameraException:

• In CameraViewHandler.Dispose(), cameraProvider.Dispose() is called. However, cameraProvider is registered as a singleton:
  

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

  Line 25 in 6c4f103

  builder.Services.AddSingleton<ICameraProvider, CameraProvider>();

When the user navigates away from a CameraView triggering CameraViewHandler.Dispose(), the cameraProvider will be disposed. If the app calls CameraProvider.RefreshAvailableCameras() after this point, a ObjectDisposedException will be thrown:

Code changes

• In CameraManager.UpdateCaptureResolution, exit the method when cameraView.SelectedCamera is null, instead of throwing an exception.
• Remove cameraProvider.Dispose() in CameraViewHandler.Dispose(). (Since cameraProvider is a singleton, I'm not sure where is an appropriate place to call cameraProvider.Dispose() , but the current code should definitely be removed)

Linked Issues

• Fixes #

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls

Additional information

[Copilot]

Pull Request Overview

This PR fixes critical regression issues introduced in PR #2909 that cause the CameraView to crash. The root cause involves a timing issue where UpdateCaptureResolution() is called during initialization before SelectedCamera is set, and improper disposal of a singleton cameraProvider.

Key Changes:

• Modified UpdateCaptureResolution() to gracefully handle null SelectedCamera by returning early instead of throwing exceptions
• Removed premature disposal of singleton cameraProvider in CameraViewHandler.Dispose()

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
CameraViewHandler.shared.cs	Removed disposal of singleton cameraProvider to prevent ObjectDisposedException
CameraManager.windows.cs	Combined null checks and removed exception throw for null SelectedCamera
CameraManager.macios.cs	Combined null checks and removed exception throw for null SelectedCamera

[zhitaop]

@TheCodeTraveler This PR aims to fix 2 regressions introduced by #2909, could you please have a look?

[Copilot]

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[Copilot]

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[TheCodeTraveler]

Thanks @zhitaop - good catch!