[camera]fix a crash when switching camera while recording due to disconnected capturePhotoOputput by hellohuanlin · Pull Request #13248 · flutter/packages

hellohuanlin · 2026-10-14T04:05:33Z

This PR fixes one of the test failures here flutter/flutter#191202. This failure is not iOS 27 specific. However, since it requires physical device (switch between front/back camera), it is not run on our CI, so we didn't catch it.

How was it broken

Before switching camera, the capture session has:

Inputs:       [ backCameraInput ]
Outputs:      [ captureVideoOutput, capturePhotoOutput ]
Connections:
  Wire 1: backCameraInput  -> captureVideoOutput   (created manually via addConnection)
  Wire 2: backCameraInput  -> capturePhotoOutput   (created automatically via addOutput)

When switching camera input (from back camera to front camera), we remove video input and output, but left photo output untouched. So at this point the capture session has:

Inputs:       [ ]
Outputs:      [ capturePhotoOutput ]   <-- still in the session, but unplugged!
Connections:  [ ]                      <-- both Wire 1 and Wire 2 were deleted!

Now when adding back the camera input, we simply do:

videoCaptureSession.addInputWithNoConnections(captureVideoInput)
videoCaptureSession.addOutputWithNoConnections(captureVideoOutput.avOutput)

So our capture session ends up with:

Inputs:       [ frontCameraInput ]
Outputs:      [ capturePhotoOutput, newVideoOutput ]
Connections:
  Wire 1: frontCameraInput -> newVideoOutput
  Wire 2: (MISSING! capturePhotoOutput has no wire to frontCameraInput!)

Then a subsequent code calls

capturePhotoOutput.maxPhotoDimensions = maxSupportedDimensions

Which throws NSInvalidArgumentException because it has no connection.

The fix is simply to use addInput rather than addInputWithNoConnections, which would automatically add the frontCameraInput -> capturePhotoOutput connection.

Fixes flutter/flutter#194344

List which issues are fixed by this PR. You must list at least one issue.

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gemini-code-assist

Code Review

This pull request addresses a crash when switching cameras during video recording by ensuring the photo output is reconnected. Specifically, DefaultCamera.swift is updated to use addInput instead of addInputWithNoConnections when switching video inputs. To support this, mock classes for the capture session and photo output are enhanced, and a new test is added to verify the reconnection and updating of photo dimensions. The review feedback points out a missing return statement in the error handling blocks of DefaultCamera.swift which could trigger multiple completion calls, and suggests refining the mock removeInput implementation to only remove connections associated with the removed input.

gemini-code-assist · 2026-10-14T04:07:02Z

    }
-    videoCaptureSession.addInputWithNoConnections(captureVideoInput)
+
+    // Do not use addInputWithNoConnections. The session still has the disconnected
+    // capturePhotoOutput, and we need to reconnect it to the captureVideoInput.
+    videoCaptureSession.addInput(captureVideoInput)


There is a missing return statement inside the if !videoCaptureSession.canAddInput(captureVideoInput) block. Without an early return, the method will continue executing, attempting to add the input and eventually calling completion(.success(())) even after a failure has already been reported. This violates the platform channel protocol (calling the completion handler multiple times) and can lead to unexpected behavior or crashes.

Please also apply this fix to the subsequent canAddOutput and canAddConnection checks in this method, as they suffer from the same missing return issue.

Suggested change

}

videoCaptureSession.addInputWithNoConnections(captureVideoInput)

// Do not use addInputWithNoConnections. The session still has the disconnected

// capturePhotoOutput, and we need to reconnect it to the captureVideoInput.

videoCaptureSession.addInput(captureVideoInput)

return

}

// Do not use addInputWithNoConnections. The session still has the disconnected

// capturePhotoOutput, and we need to reconnect it to the captureVideoInput.

videoCaptureSession.addInput(captureVideoInput)

Good find! This is an existing bug, so filed flutter/flutter#194348

Also simply adding the return doesn't balance out the beginConfiguration() call, so the suggestion is wrong.

cc @RobertOdrowaz

gemini-code-assist

Code Review

This pull request modifies DefaultCamera.swift to use addInput instead of addInputWithNoConnections when switching video inputs during recording, ensuring the disconnected photo output is reconnected. It also enhances mock classes (MockCapturePhotoOutput, MockCaptureSession) and adds a unit test to verify this behavior. Feedback points out a missing return statement in the error handling block for canAddInput (and potentially subsequent checks) in DefaultCamera.swift, which could lead to multiple completion calls and crashes.

cbracken

flutter/packages@da40eaf...93eede7 2026-10-16 [email protected] [camera]fix a crash when switching camera while recording due to disconnected capturePhotoOputput (flutter/packages#13248) 2026-10-16 [email protected] [various] Update iOS example apps to the 15.0 deployment target (flutter/packages#13223) 2026-10-16 [email protected] [material_ui] Add M3E `IconButton` example (flutter/packages#13085) 2026-10-15 [email protected] [ci] Increase deprecation check minimum to iOS 16 (flutter/packages#13211) 2026-10-15 [email protected] [google_sign_in] Remove the public iOS handleOpen helper (flutter/packages#13273) 2026-10-15 [email protected] [google_fonts] Make the pendingFonts test deterministic (flutter/packages#13262) 2026-10-15 [email protected] [vector_graphics_compiler] Fix tspan transform applied twice (flutter/packages#13129) 2026-10-15 [email protected] Roll Flutter from 426be96 to 5c7e45a (21 revisions) (flutter/packages#13270) 2026-10-15 [email protected] [flutter_svg] Add golden widget tests for SVG alpha masks (flutter/packages#13245) If this roll has caused a breakage, revert this CL and set the roller to dry run mode using the controls here: https://autoroll.skia.org/r/flutter-packages-flutter-autoroll Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

flutter-dashboard Bot added the CICD Run CI/CD label Oct 14, 2026

github-actions Bot added p: camera platform-ios platform-macos labels Oct 14, 2026

gemini-code-assist Bot reviewed Oct 14, 2026

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Comment thread ...mera_avfoundation/darwin/camera_avfoundation/Sources/camera_avfoundation/DefaultCamera.swift Resolved

hellohuanlin force-pushed the switch_camera_while_recording_crash branch from b69597f to be090e5 Compare October 14, 2026 04:08

hellohuanlin mentioned this pull request Oct 14, 2026

[camera]missing a return after flutterError flutter/flutter#194348

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hellohuanlin force-pushed the switch_camera_while_recording_crash branch from be090e5 to e7f84c4 Compare October 14, 2026 04:21

hellohuanlin requested review from cbracken and vashworth October 14, 2026 18:28

cbracken approved these changes Oct 16, 2026

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[camera]fix a crash when switching camera while recording

ed63b2d

hellohuanlin force-pushed the switch_camera_while_recording_crash branch from 1859f73 to ed63b2d Compare October 16, 2026 03:15

hellohuanlin added the autosubmit Merge PR when tree becomes green via auto submit App label Oct 16, 2026

auto-submit Bot merged commit 93eede7 into flutter:main Oct 16, 2026
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engine-flutter-autoroll mentioned this pull request Oct 16, 2026

Roll Packages from da40eaf4548a to 93eede7768d6 (9 revisions) flutter/flutter#194564

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hellohuanlin mentioned this pull request Oct 20, 2026

[ios] Consider running some iOS integration tests (such as camera) on real devices flutter/flutter#194884

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[camera]fix a crash when switching camera while recording due to disconnected capturePhotoOputput - #13248

[camera]fix a crash when switching camera while recording due to disconnected capturePhotoOputput#13248
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hellohuanlin commented Oct 14, 2026

How was it broken

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