Why does HorizontalPager's automatic scrolling stop after manual scrolling? - kotlin

Question

I have a HorizontalPager
val pageCount = bannerList.size
val startIndex = Int.MAX_VALUE / 2
val pagerState = rememberPagerState(initialPage = 100)
HorizontalPager(
count = Int.MAX_VALUE,
state = pagerState,
contentPadding = PaddingValues(
horizontal = 20.dp
),
modifier = Modifier
.fillMaxWidth()
) { index ->
// content goes here
}
and I made it scrolling every 4 second like banners with LaunchedEffect
LaunchedEffect(
key1 = Unit,
block = {
repeat(
times = Int.MAX_VALUE,
action = {
delay(
timeMillis = 4000
)
pagerState.animateScrollToPage(
page = pagerState.currentPage + 1
)
}
)
})
it scrolls fine every 4 second but when i scroll it manually HorizontalPager stops scrolling!
any suggestions how to fix this?

Answer 1

animateScrollToPage throws an exception when called during manual scrolling:
java.util.concurrent.CancellationException: Current mutation had a higher priority
You can solve it in many ways. For example just catch the exception and ignore it:
delay(
timeMillis = 4000
)
try {
pagerState.animateScrollToPage(
page = pagerState.currentPage + 1
)
} catch (_: Throwable) {
}
An other option is to check whether the pager is being dragged and stop your LaunchedEffect for this period of time:
val isDragged by pagerState.interactionSource.collectIsDraggedAsState()
if (!isDragged) {
LaunchedEffect(Unit) {
// ...
}
}
I think the second solution is cleaner, because in this case the timer will be restarted, and delay until the next scroll will always be the same.