[camera_android] Reset AE and AF triggers to idle after capture

[q2a3z]

Issue

App freezes during focus/flash sequence in low light.
On high-end camera devices, focusing takes longer in dark environments. Repeatedly requesting focus while using the flash can cause the CaptureRequest to hang.

The issues has been resolved.
I reproduced the same behavior on a different device (not an Xperia).

This log has been captured on my Xperia device.

D/CameraCaptureCallback(12647): CameraCaptureCallback | state: STATE_CAPTURING | afState: 1 | aeState: 5
D/CameraCaptureCallback(12647): CameraCaptureCallback | state: STATE_CAPTURING | afState: 1 | aeState: 5
D/CameraCaptureCallback(12647): CameraCaptureCallback | state: STATE_CAPTURING | afState: 5 | aeState: 4
D/CameraCaptureCallback(12647): CameraCaptureCallback | state: STATE_CAPTURING | afState: 5 | aeState: 4
D/CameraCaptureCallback(12647): CameraCaptureCallback | state: STATE_CAPTURING | afState: 1 | aeState: 4
I/Camera  (12647): refreshPreviewCaptureSession

Root Cause

Camera2 trigger controls are driven by one-shot states (START), but they are not always reset to IDLE once the sequence is complete. On certain devices (like the Xperia 1), this failure to reset can block subsequent capture requests.

Fix

runPrecaptureSequence():
Send an AE trigger START, then immediately follow with IDLE in the same execution path.

lockAutoFocus():
Send an AF trigger START, then reset to IDLE after the preview request is captured.

Results

AE/AF triggers are now consistently returned to the IDLE state.
The freeze during capture after using the flash on Xperia 1 has been resolved.
Camera trigger sequences are now stable across various device models.

---

By the way,

I believe CameraX is the way to go for Android camera development. It's been the default since version 0.11.0.

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[gemini-code-assist]

Code Review

The pull request modifies the Camera.java file to explicitly reset camera capture triggers to an idle state. Specifically, it adds code to reset CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER to IDLE after runPrecaptureSequence and CaptureRequest.CONTROL_AF_TRIGGER to IDLE after lockAutoFocus, ensuring proper state management for auto-exposure and auto-focus operations.

[camsim99]

Thanks for working on this fix! At a high level, this makes sense to me, but there's two things I want to address:

1: The main concern that I have is that CameraCaptureSession.capture is an asynchronous call, so I worry we may be resetting the AE and AF triggers back to idle too soon potentially. Can you clarify if this is true? If so, a solution may be to provide a callback to set the triggers to idle.

2: In order to land this, we will need tests for this change. A good place to add them would be in CameraTest.java.

[q2a3z]

@camsim99

Thank you for the quick reply and the suggestions.

Yap, I also thought it might be an async function. It seems like the flash turns off just a split second before the photo is captured. I'll try your suggestion and let you know as soon as I have any updates.

Once I've finished checking step 1, I’ll add some tests to CameraTest.java.