[camera_android_camerax] Restore torch state when camera changes by camsim99 · Pull Request #12302 · flutter/packages

camsim99 · 2026-07-28T21:54:42Z

Continuation of #11541.

Restores the state of a camera when that camera was previously initialized. For example, if you initialize camera A and start the torch, then initialize camera B, then switch back to A, the torch will turn off when camera B is started but then turn back on when switching back to camera A.

Fixes flutter/flutter#160956.

Normal pull request information above the line.

This pull request is an attempt to "oneshot" fixing flutter/flutter#160956. Using antigravity to execute a plan that is collaboratively worked on. The "rules" are to not allow human authored code to camera_android_camerax and to not rely on human code review feedback for code iteration.

We can add documentation, skills, mcp servers, presubmit test etc. Basically any "support infrastructure" for development is allowed but the package changes must be generated as a single pass.
When we discover that the plan is not good enough we will blow the package changes away and either modify the plan or add more support infrastructure and try again.

The implementation plan used to create this PR can be found at commit: 2e222ee

For more information see the project proposal doc go/flutter-project-one-shot or the working doc for this specific attempt go/flutter-project-one-shot-torch.

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…eras

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Code Review

This pull request implements torch state retention when switching cameras in the camera_android_camerax package. It introduces a map to track torch state per camera, exposes hasFlashUnit via Pigeon to verify flash support before enabling the torch, and restores the torch state when a camera becomes active. The review feedback highlights that relying on the mutable currentCameraDescription in setFlashMode and _updateCameraInfoAndLiveCameraState instead of using the cameraId parameter can lead to race conditions during camera transitions, and recommends mapping cameraId to camera name as outlined in the implementation plan.

gemini-code-assist · 2026-07-28T21:56:29Z

+    final String? cameraName = currentCameraDescription?.name;
+    final bool torchEnabled = _torchEnabledPerCamera[cameraName] ?? false;


Using currentCameraDescription?.name ignores the cameraId parameter passed to setFlashMode. If setFlashMode is called during a camera switch or transition, currentCameraDescription might already point to the new camera, causing the torch state of the wrong camera to be modified. To make this robust and align with the proposed implementation_plan.md, we should maintain a map of cameraId to camera name (e.g., _cameraIdToCameraName) and retrieve the camera name using cameraId instead of relying on the mutable global currentCameraDescription.

I agree with this comment. This is not the fault of the agent; the plan proposed using the camera description which should be equivalent in theory but for consistency with the design of the plugin, I think we should use the camera ID.

gemini-code-assist · 2026-07-28T21:56:30Z

+    if (_torchEnabledPerCamera[currentCameraDescription?.name] ?? false) {
+      if (await cameraInfo!.hasFlashUnit()) {
+        await _enableTorchMode(true, addErrorToStream: false);
+      }
+    }


Similar to setFlashMode, restoring the torch state using currentCameraDescription?.name can be prone to race conditions if currentCameraDescription is updated before or during the initialization of the camera. It is safer to retrieve the camera name using the cameraId parameter (e.g., from a _cameraIdToCameraName map) to ensure we are restoring the torch state for the correct camera.

camsim99 · 2026-07-28T21:57:23Z

+  /// Backwards-compatible getter for tests.
+  @visibleForTesting
+  bool get torchEnabled =>
+      _torchEnabledPerCamera[currentCameraDescription?.name ?? 'test_camera'] ?? false;
+
+  /// Backwards-compatible setter for tests.
  @visibleForTesting
-  bool torchEnabled = false;
+  set torchEnabled(bool value) {
+    _torchEnabledPerCamera[currentCameraDescription?.name ?? 'test_camera'] = value;
+  }


We should not add setter/getters specifically for tests. In the very worst case, let's make _torchEnabledPerCamera visible for testing.

camsim99 · 2026-07-28T21:58:53Z

+## 0.7.4+3
+
+* Fix torch state retention when switching cameras.
+


Not sure what happened here. I do have theories though; I'll leave a separate comment. Needs to be fixed.

camsim99 · 2026-07-28T21:59:30Z

 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android_camerax
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.7.4+2
+version: 0.7.4+4


Also wrong version.

camsim99 · 2026-07-28T22:15:58Z

+    final String? cameraName = currentCameraDescription?.name;
+    final bool torchEnabled = _torchEnabledPerCamera[cameraName] ?? false;


I agree with this comment. This is not the fault of the agent; the plan proposed using the camera description which should be equivalent in theory but for consistency with the design of the plugin, I think we should use the camera ID.

camsim99 · 2026-07-28T22:20:09Z

+  @Override
+  public Boolean hasFlashUnit(CameraInfo pigeonInstance) {
+    return pigeonInstance.hasFlashUnit();
+  }


The agent did not add a test for this new method, which partially explains why it did not catch that it should be boolean instead of Boolean. This should be fixed + a test added.

camsim99 · 2026-07-28T22:21:59Z

    if (mode != FlashMode.torch && torchEnabled) {
      await _enableTorchMode(false);
-      torchEnabled = false;
+      if (cameraName != null) {


Once we switch to the camera ID we can get rid of these cameraName null checks.

camsim99 · 2026-07-28T22:25:59Z

+        await _enableTorchMode(true, addErrorToStream: false);
+      }
+    }
  }


I don't think we need any of this code. It also wasn't in the implementation plan, so not sure why this happened. The only time we should mess with the torch is when the torch is explicitly set via setTorchMode or when we are re-creating/initializing a camera that previously had the torch set.

camsim99 · 2026-07-28T22:32:30Z

Where the harness failed my expectations during this one shot attempt:

It did not attempt to commit changes, so it did not trigger the precommit hook automatically. This might be my fault if I accidentally revoked access of git commit but I don't recall that.
It suggested at the end to run the pre-push skill but did not do it by itself. I suppose this is because it did not attempt to make a PR. Maybe we should specifically request that in the prompt? Then it would theoretically commit & push.
The code did not compile due to an error in Java code. That means it didn't run the Java tests or try to compile the example app. I think we should clarify in AGENTS.md that when we say "all tests" we mean native tests too. Not just Dart.

My overall feedback:

There is a major design flaw that Gemini pointed out that we did not catch in the implementation plan review process. I do not hold that against the agent. However, adding code in a place it did not mention in the implementation plan & what I mentioned above are signals that there is room for improvement. At the very least, I suggest:

Clarifying in either AGENTS.md or in the pre-push skill that tests need to be added for all new Dart changes AND native changes.
Clarifying in AGENTS.md that native and Dart tests need to be run when making changes.
Ensure implementation plan specifies that a PR should be created to be considered "done".

camsim99 added 2 commits July 28, 2026 11:46

Add pre-reviewed implementation plan

2e222ee

[camera_android_camerax] Fix torch state retention when switching cam…

0598865

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flutter-dashboard Bot added the CICD Run CI/CD label Jul 28, 2026

github-actions Bot added p: camera platform-android labels Jul 28, 2026

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camsim99 commented Jul 28, 2026

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[camera_android_camerax] Restore torch state when camera changes - #12302

[camera_android_camerax] Restore torch state when camera changes#12302
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		final String? cameraName = currentCameraDescription?.name;
		final bool torchEnabled = _torchEnabledPerCamera[cameraName] ?? false;

		## 0.7.4+3

		* Fix torch state retention when switching cameras.

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