The Camera2Renderer Android class does not rotate the preview image if the camera's sensor is rotated (this can happen with some smartglasses, e.g. with the Vuzix M300 where the sensor is mounted upside-down). The result is that the preview image is rotated by 180 degrees.

The Camera2Sample by Android uses

 characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);

to query the sensor rotation and

activity.getWindowManager().getDefaultDisplay().getRotation();

to query the display rotation but I did not succeed in integrating this into OpenCV's Camera2Renderer.