I am working on a auto scroller for my horizontal pager. Is should auto scroll every 3 seconds. Should be able to skip when clicked. And pause when longClicked. When in the paused state. It will resume when the user swipes or clickes to skip. However, my isPaused state always seems to be false in the LaunchedEffect. I think there is something wrong with the way I am handling my state.

I set the isPaused to intialize as false. As we are not paused when first entering the screen

When longClicked I set the isPaused to true

And to resume in the click or swipe I set back to false.

This looks strange as I set to true, but the LaunchedEffect gets triggered twice, and is false

onLongClick true
LaunchedEffect false
LaunchedEffect false

    val coroutineScope = rememberCoroutineScope()
    var isPaused by remember { mutableStateOf(false) }
    LaunchedEffect(isPaused) {
        println("LaunchedEffect $isPaused")
        
        while (!isPaused) {
            delay(3_000)
            var nextPage = pagerState.currentPage + 1
            if (nextPage >= items.count()) {
                nextPage = 0
            }
            pagerState.animateScrollToPage(nextPage)
        }
    }

My horizontal pager looks like this

HorizontalPager(
            state = pagerState,
            pageSpacing = 16.dp,
            modifier = modifier
                .fillMaxSize()
                binedClickable(
                    onLongClick = {
                        isPaused = true
                        println("onLongClick $isPaused")
                    },
                    onClick = {
                        if(pagerState.currentPage < items.count()) {
                            isPaused = false
                            println("onClick $isPaused")
                            coroutineScope.launch {
                                pagerState.animateScrollToPage(pagerState.currentPage + 1)
                            }
                        }
                    }
                )
        ) { pageIndex ->
            when(pageIndex) {
                in items.indices -> {
                    isPaused = false
                    content(items[pageIndex])
                }

                else -> {
                    lastItemContent?.invoke()
                }
            }
        }

I am working on a auto scroller for my horizontal pager. Is should auto scroll every 3 seconds. Should be able to skip when clicked. And pause when longClicked. When in the paused state. It will resume when the user swipes or clickes to skip. However, my isPaused state always seems to be false in the LaunchedEffect. I think there is something wrong with the way I am handling my state.

I set the isPaused to intialize as false. As we are not paused when first entering the screen

When longClicked I set the isPaused to true

And to resume in the click or swipe I set back to false.

This looks strange as I set to true, but the LaunchedEffect gets triggered twice, and is false

onLongClick true
LaunchedEffect false
LaunchedEffect false

    val coroutineScope = rememberCoroutineScope()
    var isPaused by remember { mutableStateOf(false) }
    LaunchedEffect(isPaused) {
        println("LaunchedEffect $isPaused")
        
        while (!isPaused) {
            delay(3_000)
            var nextPage = pagerState.currentPage + 1
            if (nextPage >= items.count()) {
                nextPage = 0
            }
            pagerState.animateScrollToPage(nextPage)
        }
    }

My horizontal pager looks like this

HorizontalPager(
            state = pagerState,
            pageSpacing = 16.dp,
            modifier = modifier
                .fillMaxSize()
                binedClickable(
                    onLongClick = {
                        isPaused = true
                        println("onLongClick $isPaused")
                    },
                    onClick = {
                        if(pagerState.currentPage < items.count()) {
                            isPaused = false
                            println("onClick $isPaused")
                            coroutineScope.launch {
                                pagerState.animateScrollToPage(pagerState.currentPage + 1)
                            }
                        }
                    }
                )
        ) { pageIndex ->
            when(pageIndex) {
                in items.indices -> {
                    isPaused = false
                    content(items[pageIndex])
                }

                else -> {
                    lastItemContent?.invoke()
                }
            }
        }

• android
• android-jetpack-compose

• 1 You are setting isPaused = false inside the pager content block. This causes isPaused always false – Abdo21 Commented Nov 16, 2024 at 11:46

1 Answer 1

The problem lies within this code bit:

in items.indices -> {
    isPaused = false  // HERE
    content(items[pageIndex])
}

Whenever a recomposition of the content of HorizontalPager occurs, isPaused will be reset to false.
To set isPaused to false only when the user manually is swiping, you can use another LaunchedEffect like this:

LaunchedEffect(pagerState.currentPage) {
    isPaused = false
}

The content might get recomposed whenever the isPaused changes because the whole HorizontalPager is within the same recomposition scope.