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Posted on by Daniel_Basham

I'm trying to create an app that requires and input and displays that input on another screen

however I want to use another instance of the app on the secondary screen.

Is this possible?

Basically I want to input 2402123 and on a monitor in another building i want them to see that number without having to do a thing.

Is this possible? can an instance of the app be updated from another instance?

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Building Power Apps

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Pstork1 69,665 Most Valuable Professional on at

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If you store a value in a backend data source then that value can be viewed in another instance of the app connected to that data source. The only issue is that there is no way to push the change from the data source to the second copy of the app. The second copy has to refresh its connection to get the update. You can do that with a timer that automatically refreshes the app. But doing that too frequently will impact performance of the app. I wouldn't want to have it update more than once every 3-5 minutes.
Daniel_Basham 10 on at

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It would only hold the most basic information for instance I want to be able to input a number and have that number displayed autonomously across the building on another computer / monitor. I need it to be able to be run up to 10 hours at a time and be update on average 30 times a day. However, I can't rely on 3-5 minutes of down time between each up-date I need it to be close to instant no more than 30 seconds.
Daniel_Basham 10 on at

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I've created a shortcut to the PowerApps that I've put into the startup / boot folder of the machine so when it turns on it automatically opens the app in kiosk mode so no input is needed to get to the app. My app is a dual screen app, 1 screen is for the displays and 1 screen is for the input of the numbers to the other displays. At any given moment I expect 4 displays to be running and 1 input at the same time.
Pstork1 69,665 Most Valuable Professional on at

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As I said, the problem is that when you update the data source on one device it will not update the value on other devices until that device updates its connection to the data source. There is no way in Power Apps for a connection to PUSH changes to a device. Changes must be pulled by a device. So you need some mechanism on the remote devices to refresh the screen. As I mentioned you can have a timer that repeats and does that refresh. But doing that every 30 seconds on multiple devices is going to create a lot of traffic and will probably impact your performance.
RandyHayes 76,299 Super User 2024 Season 1 on at

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@Daniel_Basham

Actually, little known aspect of PowerApps, you can do semi-real time without refreshing datasources in your app (which is performance expensive!) App-to-app time-to-reflect is typically a second, but could be as long as several seconds to reflect.

What is your Datasource in your scenario?
Daniel_Basham 10 on at

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I dont have a datasource currently, Im still in the brainstorm aspect of the app.
Which means it could be in any data source, SharePoint, Excel anything.
Do you have a suggestion as to a specific one?
Daniel_Basham 10 on at

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Nothing needs to be stored everything can be deleted once shown.
Its an extremely simplistic app just needs to store 1 number and once Im done with that number and need to show a different number it can be deleted.
RandyHayes 76,299 Super User 2024 Season 1 on at

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@Daniel_Basham

So, you'll need an intermediary datasource to do this. I would recommend a simple list in SharePoint.

Here is a starter:

1) Create a list - call it what you want, but for this sample, I will call it interList

2) Create an app. Connect to that list as a datasource.

3) Add a timer with a duration of 1000 (1 second) and autorepeat turned on and autostart turned on.

4) Set the OnEnd action of the timer formula to: UpdateContext({lclID: Blank()}); UpdateContext({lclID: 1})

5) Place a label on the screen and set the Text property to: LookUp(interList, ID=lclID, Title)

Run your app!

Change the Title of the first record (record ID) in your list to whatever you want. The app will reflect it almost immediately.

The above could be a simple "display" app.

If you want some other app to change the value, you could do that as well, or you could simply change the value directly in the list.
Pstork1 69,665 Most Valuable Professional on at

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@RandyHayes With all due respect. You are using a timer to do a Lookup() against a backend data source, which is essentially the same thing I told him earlier. Its not an app to app communication. Its a timer refreshing a control that is pulling an updated value from a backend data source.
RandyHayes 76,299 Super User 2024 Season 1 on at

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@Pstork1

Sort of! But this is much different. The timer actually only has one purpose - to cause the Lookup to lookup a different record, then lookup the normal one.

To be clear though - there is NO refresh needed.

Your point about the app to app communication is valid. There is no push to the app. But the method laid out here is more about utilizing the session table feature (that is not published and little known) whereby it will get the most recent record if the record is no longer referenced in the app.

Meaning - if you have nothing in your app that is bound to record x, then when you do reference it, it will be the current datasource value. If you lose that reference and then reference it again, it will be the most current value. So, if updated by another means (another app, flow/PowerAutomate, direct change, etc.) it will reflect that changed value and no refresh was issued to get it.

For so long the rule has always been - if something changes the datasource record, then you HAVE to refresh the datasource in the app to get the new value, but that is not a true statement any longer.

So, again, yes, it is not a push to an app, but it is a simulated way to do that and it carries NO overhead like a refresh would. The update of the data (what is seen in the app) is all done at the session table level and not the app level. So, the performance does not suffer like a refresh causes.