Timing in PowerApps

I keep the PDFs in a SharePoint document library and use ItemId as a key.



And resulting the app looks like this:



Of course I need to filter the SharePoint list to only show entries related to the current item, and I added the following to OnStart of the app, like described on docs:

If(!IsBlank(Param("EntityId")), Set(FinOpsInput, Param("EntityId")), Set(FinOpsInput,""));

And here is what I have put in Items of the Gallery showing the SharePoint data:

If(!IsBlank(FinOpsInput),SortByColumns(Filter(ProductPDFs,ItemId=FinOpsInput),"ItemId",Ascending),SortByColumns(ProductPDFs,"ItemId",Ascending))

A problem I have spent hours on, was that the filtering was very flaky. Sometimes it would flicker, showing all my items and then apply the filter, and sometimes it just didn't apply the filter until I manually refreshed the list.

It seems like things run i parallel when you open an app, so it would actually start to load data from SharePoint before or while the OnStart trigger is executed. And in some cases it wouldn't know about the FinOpsInput variable yet when applying my filter.

A solution could be to add a variable to OnStart, letting you know if that is finished, and make a bogus filter until it is done. Like this:

If(!IsBlank(Param("EntityId")),Set(FinOpsInput,Param("EntityId")),Set(FinOpsInput,""));Refresh(ProductPDFs);Set(AppIsStarted, true)

And change Items of the gallery to this:
If (AppIsStarted, If(!IsBlank(FinOpsInput),SortByColumns(Filter(ProductPDFs,ItemId=FinOpsInput),"ItemId",Ascending),SortByColumns(ProductPDFs,"ItemId",Ascending)), Filter(ProductPDFs,ItemId="BOGUS"))

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