Nested gallery shows before hiding itself

[morgan_s]

Hi all - I have a gallery that has dynamic height settings.  Inside there is a nested gallery that I've coded visibility to show when it has items in the gallery like so:  

If(CountRows(Self.AllItems) > 0, true, false)

The nested gallery has a filter on it that populates based on the item value of the parent gallery which is a collection of dates based on a ForAll function.

The problem I have, is that as I scroll the parent list and the gallery lazy loads - each nested gallery populates with all the items (not just filtered ones) then hides itself based on the visibility & filter functions, so it flashes on screen for half a second before disappearing on its own.  It only occurs once when the items in the parent gallery first scroll into view.

The user experience at present is quite jarring.  I thought a solution might be to pre-load the entire list somehow without lazy loading??  I can't see a setting to turn off lazy loading is all.  Or somehow set an initial state on the nested controls to be hidden,  then show based on the rowcount, but unsure if this is possible either.  Any suggestions welcome.  

[Amik]

@morgan_s - could share code used in the items property for both parent gallery and child gallery.

[morgan_s]

Hey @Amik see below for parent gallery:

ForAll(Sequence(366),Value + varCurrentDate)

and nested gallery (pulls from a sharepoint list):

Filter('Communications Schedule Import', 'Send Date' = ThisItem.Value, 'Department ID' in DeptIDs)

[Amik]

Hi @morgan_s ,

As I understand it. You have a nested gallery. The parent gallery is displaying all items, irrespective of whether that item exists based on your filtering criteria in the child gallery.

You want to hide any item in the parent gallery which does exist in the child gallery based on your filtering criteria.

I suspect I might be misunderstanding, but do really you need to apply a boolean condition like "CountRows(Self.AllItems) > 0" onto the visible property when you could just configure the parent gallery to exclude anything which does not exist in the child gallery?

For example, in your parent Gallery, you could include only items where there is a matching date:

Filter(
    'Communications Schedule Import',
    'Send Date' in ForAll(
        Sequence(366),
        Value + varCurrentDate
    )
)

And then in your child gallery, carry on with your filter criteria but exclude the date condition:

Filter(
    'Communications Schedule Import',
    'Department ID' in DeptIDs
)

------------------------------------------------------------------------------------------------------------------------------------

If I have answered your question, please mark your post as Solved.

If you like my response, please give it a Thumbs Up.

[morgan_s]

Hey @Amik , yes not quite what I needed sorry but thanks for helping. 

I still want to show the parent items, the problem is I want to hide the child item if its empty.  Which it does do, but for some reason it flashes on screen temporarily during scrolling before it hides.  It feels like the filter code executes only after a 'select all' from the sharepoint list, and too slowly for the presentation layer to catch it.  Just a guess tho.

[Amik]

hi @morgan_s - I have a few apps which make use of nested galleries. One of them has about a dozen components in the child gallery (10 shapes and several fields per item), but I do not experience the flashing issue you have mentioned. The only issue is that there is a 1 second delay when scrolling (which we have found acceptable).

Is there anything else going on in the configuration of those Galleries you may have not mentioned? Will be difficult to diagnose without going into the detail.

Also, not a solution but it is worth looking into grouped galleries. Nested galleries are good when you expect the items in the child gallery to be small, but the performance will not be scalable when you go beyond dozen rows per item.

https://www.matthewdevaney.com/group-the-items-in-a-power-apps-gallery/