Can't activate the flash after entering multi tasking

Processing for Android
1

I made this simple code for activating and deactivating the flash of the phone and it’s working fine, but when i go in the multi tasking and then i re-enter in the app (without closing it) I can’t manage to re-activate the flash. I’m using Ketai library and I have allowed the permission to camera. This is the code:

import ketai.camera.*;

PImage flashOn;
PImage flashOff;
KetaiCamera cam;

void setup()
{
  imageMode(CENTER);
  cam = new KetaiCamera(this, 320, 240, 24);
  cam.start();
  flashOn = loadImage("flashOn.png");
  flashOff = loadImage("flashOff.png");
}

void draw()
{
  background(176);

  if (cam.isFlashEnabled())

    image(flashOn, width/2, height/2, width, width);
  else
    image(flashOff, width/2, height/2, width, width);
}

void mousePressed()
{
  if (cam.isFlashEnabled())
    cam.disableFlash();
  else
    cam.enableFlash();
}

Is there a way to make the program function even after going in the multi tasking and re-entering the app?

Thanks for your help.