Whilst your Player is connected to your CMS, you can schedule a Layout. If that connection is then lost, the Player will continue to display the scheduled Layout until it receives a new schedule.
Your Default Layout for the Player will display on the Player when no other Event has been scheduled. This means that you do not have to schedule the Default Layout.
To answer your question, what is shown on your Player whilst it is offline will depend on whether it had a Layout scheduled prior to going offline. So if your Player has Layout 1 scheduled and then loses the connection to the CMS, it will continue to display the cached Layout until it is told to display something else. If there is not a Layout scheduled or the scheduled layout is not valid, The Default Layout will instead display.
From what I understand from your above scenario, You would like to display a Layout during the hours 8:00 until 20:00 and from 20:00 until 8:00 you would like a black screen. If so, there are many ways to achieve this:
For the below examples, I will call the Layout that contains the information you wish to display during opening hours Layout 1. The Layout that will display the Black screen for when the store is closed will be named Layout 2. All of the below examples would need to be scheduled prior to Players going offline.
You could set Layout 1 as your Default Layout and schedule Layout 2 to display 20:00 until 8:00. Because Layout 1 is set as Default Layout, you will not need to schedule it as it will show by default. When it is 20:00, the schedule for Layout 2 will begin and the black screen will be shown. When it is 8:00 the next morning, the schedule will end and the Player will default back to Layout 1.
You could set Layout 2 as your Default Layout and only schedule Layout 1 to show from 8:00 until 20:00. When it is 20:00, the schedule will end and the Default Layout (Layout 2) will automatically display. When it is 8:00, the schedule will begin again and Layout 1 will be shown.
You could schedule Layout 1 from 8:00 until 20:00, and schedule Layout 2 from 20:00 until 8:00. With this option, you would be able to set a third Layout as your Default Layout instead. The Default Layout is often used to indicate if there is something wrong with your schedule/Player. For example if for some reason there was an issue with the Player and it was unable to display your scheduled Events, it will instead display your Default Layout. This can be very helpful when troubleshooting an issue as in this scenario the Default Layout should never show.
Any of the above options will provide you the result you are looking for, I would personally recommend the Third option as this will help to identify an issue with the Player/schedule much more clearly than using the Default Layout as part of your schedule would.
Whilst I’m sure you’re already aware, your Layouts must include at least one region, which must also contain at least one item. I mention this regarding the Black screen layout you are considering making, as you will need to create a single large region that covers the entire layout and contains a black image. Simply setting the Background to black will not work as this would not include a Region in the Layout.
As you are using Android Players, you will also need to consider that the Players will need to be able to connect to the License Pool server occasionally to continue to be Licensed. A possible solution to this would be to use an On Premise Licensing Module or to connect your Player periodically to ensure the Player continues to be licensed.
I have included a link below to our Android Licensing Guide, which explains in more detail how this is done as well as your options for making sure the License is retained by the Player.
My apologies for the long message, I hope the above information is helpful.