Android Camera2 - Switch flash mode

Question

I'm trying to develop an application, based on Google Camera2Basic example, that uses Camera 2 API. I would like to add a button that allows me to switch the flash mode.

The problem is when I click on the button to switch between different flash modes, the captureBuilder doesn't set the correct flash mode. It is work only when I open the camera for the first time.

setFlash method:

private void setFlash(CaptureRequest.Builder requestBuilder) {
    if (mFlashSupported) {
        switch (mFlashMode) {
            case FLASH_AUTO:
                requestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
                requestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
                break;
            case FLASH_ON:
                rrequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
                requestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_SINGLE);
                break;
            case FLASH_OFF:
                requestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
                requestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
                break;
        }
    }
}

createCameraPreviewSession method:

private void createCameraPreviewSession() {
    try {
        ...

        mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
                new CameraCaptureSession.StateCallback() {

                    @Override
                    public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                        if (null == mCameraDevice) {
                            return;
                        }

                        mCaptureSession = cameraCaptureSession;
                        try {
                            mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                            setFlash(mPreviewRequestBuilder);

                            mPreviewRequest = mPreviewRequestBuilder.build();
                            mCaptureSession.setRepeatingRequest(mPreviewRequest,
                                    mCaptureCallback, mBackgroundHandler);
                        } catch (CameraAccessException e) {
                            ...
                        }
                    }

                    @Override
                    public void onConfigureFailed(
                            @NonNull CameraCaptureSession cameraCaptureSession) {
                        ...
                    }
                }, null
        );
    } catch (CameraAccessException e) {
        ...
    }
}

captureStillPicture method:

private void captureStillPicture() {
    try {
        final CaptureRequest.Builder captureBuilder =
                mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
        captureBuilder.addTarget(mImageReader.getSurface());

        captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
        setFlash(captureBuilder);

        CameraCaptureSession.CaptureCallback CaptureCallback
                = new CameraCaptureSession.CaptureCallback() {

            @Override
            public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                           @NonNull CaptureRequest request,
                                           @NonNull TotalCaptureResult result) {
                unlockFocus();
            }
        };

        mCaptureSession.stopRepeating();
        mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

unlockFocus method:

private void unlockFocus() {
    try {
        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);
        mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback,
                mBackgroundHandler);
        // After this, the camera will go back to the normal state of preview.
        setFlash(mPreviewRequestBuilder);
        mState = STATE_PREVIEW;
        mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback,
                mBackgroundHandler);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

How could I fix this problem?

Thank you.

Answer 1

You need to make sure you call

mPreviewRequest = mPreviewRequestBuilder.build();
mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback,
            mBackgroundHandler);

or equivalent after you update the request builder's flash mode. The request builder just creates requests - you still have to send them to the camera once you've set the new values you want.