firstItem doesn't work as expected

[gvenk]

I'm using the flatlist branch and it looks like the firstItem isn't working. If I set it to something different than 0, the list is displayed on the correct position, but the item isn't rendered. If I start scrolling the list, it appears.

This doesn't happen on the iOS emulator, only on a real device.

For the rest everything is working just fine! Great work on the FlatList implementation!

[gvenk]

It appears to be rather random, sometimes this will happen and sometimes not. Like it's some kind of timing issue?

[bd-arc]

Hi @gvenk,

I'm afraid that this is a bug of the FlatList component itself. See issues #1831, #13202 and #13316.

One thing that could help is adding removeClippedSubviews={false} to the <Carousel />. Unfortunately, it might take a toll on performance...

You can also try playing with the following props from VirtualizedList and FlatList's docs: initialNumToRender, maxToRenderPerBatch, windowSize and updateCellsBatchingPeriod.

Let me know if any of this tips helped regarding the issue!

[gvenk]

Thanks for the info. Unfortunately all the tips from the mentioned issues didn't result in a completely working list.
I tricked the list by setting the firstItem to the actual firstitem - 1 and then use snapToItem() to scroll to the correct item. I did this in componentDidMount() but I had to use a timeout of 250msec otherwise it's not working.
Not a solution I'm totally happy with, but for now it's working.

[bd-arc]

@gvenk That's the unfortunate tradeoff of migrating to FlatList: some issues are not resolved yet. You idea is indeed a hack, but it seems like the only solution at the moment.

Note that the 250 ms timeout might be linked to the new prop apparitionDelay (its default value being... 250 ms). You can change it to suit your needs.

[gvenk]

Yes, I'll experiment a bit with apparitionDelay, but for now it's working good enough I think.

Thanks!