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Fix connect camera cancellation #3172

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Fix connect camera cancellation #3172

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853ccb5
Handle cancellation in CameraViewHandler
zhitaop Mar 22, 2026
1949212
clean up
zhitaop Mar 24, 2026
12abe0b
Merge branch 'main' into fix/connect-camera-cancellation
zhitaop Mar 24, 2026
05044c3
Address Copilot review
zhitaop Mar 24, 2026
054921a
Merge branch 'main' into fix/connect-camera-cancellation
zhitaop Mar 30, 2026
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38 changes: 35 additions & 3 deletions src/CommunityToolkit.Maui.Camera/Handlers/CameraViewHandler.shared.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@ namespace CommunityToolkit.Maui.Core.Handlers;
/// </summary>
public partial class CameraViewHandler : ViewHandler<ICameraView, NativePlatformCameraPreviewView>, IDisposable
{
CancellationTokenSource? cts;
bool isDisposed;

/// <summary>
/// The currently defined mappings between properties on the <see cref="ICameraView"/> and
/// properties on the <see cref="NativePlatformCameraPreviewView"/>.
Expand Down Expand Up @@ -82,9 +85,29 @@ void Init(ICameraView view)
/// <inheritdoc/>
protected override async void ConnectHandler(NativePlatformCameraPreviewView platformView)
{
base.ConnectHandler(platformView);

await CameraManager.ConnectCamera(CancellationToken.None);
cts?.Cancel();
using var newCts = cts = new();
try
{
base.ConnectHandler(platformView);
await CameraManager.ConnectCamera(newCts.Token);
}
catch (OperationCanceledException) when (newCts.IsCancellationRequested)
{
// Catch and ignore the OperationCanceledException if it was caused by our own cancellation token,
// e.g. the handler is disconnected before the camera connection process completes.
}
catch (Exception)
{
DisconnectHandler(platformView);
}
Comment on lines +100 to +103
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Copilot AI Mar 24, 2026

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ConnectHandler catches all exceptions and unconditionally calls DisconnectHandler(platformView). If the handler is already disconnecting/disposing, DisconnectHandler can throw (e.g., CameraManager field already set to null and the property throws), which defeats the goal of preventing crashes. Consider guarding this path (e.g., if cancellation was requested / handler is disposed / cameraManager is null, just return), and log the exception (Trace) for non-cancellation failures before disconnecting.

Copilot uses AI. Check for mistakes.
finally
{
if (cts == newCts)
{
cts = null;
}
}
}

/// <inheritdoc/>
Expand All @@ -103,11 +126,20 @@ protected override void DisconnectHandler(NativePlatformCameraPreviewView platfo
/// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
protected virtual void Dispose(bool disposing)
{
if (isDisposed)
{
return;
}
if (disposing)
{
cts?.Cancel();
cts = null;

cameraManager?.Dispose();
cameraManager = null;
}

isDisposed = true;
}

#if WINDOWS
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