Changing Flash setting of Android Camera 2 at runtime

Question

Basically, what I am trying to do is change the CONTROL_AE_MODE by button click in the app. The user can use AUTO flash(ON_AUTO_FLASH), turn if ON(ON_ALWAYS_FLASH), or OFF(CONTROL_AE_MODE_OFF).

In this example: https://github.com/googlesamples/android-Camera2Basic/blob/master/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.java

Line 818, they set the flash once:

// Use the same AE and AF modes as the preview.
            captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            setAutoFlash(captureBuilder);

            // Orientation
            int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));

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

                @Override
                public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                               @NonNull CaptureRequest request,
                                               @NonNull TotalCaptureResult result) {
                    showToast("Saved: " + mFile);
                    Log.d(TAG, mFile.toString());
                    unlockFocus();
                }
            };

            mCaptureSession.stopRepeating();
            mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);

And then builds the CaptureSession at line 840.

Is there a way to change the CONTROL_AE_MODE after the preview is made?

I have tried remaking the session, which kinda worked:

if(flashMode == CameraView.CAMERA_FLASH_ON){
            Log.e("CAMERA 2", "FLASH ON");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
        }else if(flashMode == CameraView.CAMERA_FLASH_OFF){
            Log.e("CAMERA 2", "FLASH OFF");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_OFF);
        }else if(flashMode == CameraView.CAMERA_FLASH_AUTO){
            Log.e("CAMERA 2", "FLASH AUTO");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        }
        mFlashMode = flashMode;
        if (mCameraCaptureSession != null) {
            mCameraCaptureSession.close();
            mCameraCaptureSession = null;
       }
  createCameraPreviewSession();

For some reason, CONTROL_AE_MODE_OFF would turn the whole preview black. I tried looking in the docs for methods to update but haven't found anything.

Any tutorials or docs is much appreciated.

Answer 1

As mentioned by @cyborg86pl when switching flash modes you should not switch CONTROL_AE_MODE . Instead you can switch between FLASH_MODE´s. Here is a working example for my case:

  when (currentFlashState) {
        FlashState.AUTO -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH)
        }
        FlashState.ON -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON)
          previewRequestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH)
        }
        FlashState.OFF -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON)
          previewRequestBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF)
        }
      }
 previewRequest = previewRequestBuilder.build()
 captureSession.setRepeatingRequest(previewRequest, captureCallback, backgroundHandler)