In camera mode, if the phone is not in vertical position, the app shows a toast that informs the user that the device should be placed in vertical position.
If the user clicks the 'back" button, the app shows another toast with the message "click BACK again to exit", but it is not visible because the previous toast is over it

The first toast should be hidden when the second one is shown and, in case the user doesn't click BACK again, the first toast should return visible again.