[英]Jetpack Compose LazyColumn programmatically scroll to Item
有沒有辦法以編程方式將LazyColumn
滾動到列表中的某個項目? 我認為可以通過提升LazyColumn
參數state: LazyListState = rememberLazyListState()
來完成,但我不知道如何更改此 state 例如在按鈕單擊時。
LazyListState
通過以下方式支持滾動 position
scrollToItem()
function,它“立即”捕捉滾動 position,animateScrollToItem()
使用 animation 滾動就像是:
val listState = rememberLazyListState()
// Remember a CoroutineScope to be able to launch
val coroutineScope = rememberCoroutineScope()
LazyColumn(state = listState) {
// ...
}
Button (
onClick = {
coroutineScope.launch {
// Animate scroll to the 10th item
listState.animateScrollToItem(index = 10)
}
}
){
Text("Click")
}
在 Compose1.0.0-alpha07中,沒有公共 API,但是LazyListState#snapToItemIndex
。
/**
* Instantly brings the item at [index] to the top of the viewport, offset by [scrollOffset]
* pixels.
*
* Cancels the currently running scroll, if any, and suspends until the cancellation is
* complete.
*
* @param index the data index to snap to
* @param scrollOffset the number of pixels past the start of the item to snap to
*/
@OptIn(ExperimentalFoundationApi::class)
suspend fun snapToItemIndex(
@IntRange(from = 0)
index: Int,
@IntRange(from = 0)
scrollOffset: Int = 0
) = scrollableController.scroll {
scrollPosition.update(
index = DataIndex(index),
scrollOffset = scrollOffset,
// `true` will be replaced with the real value during the forceRemeasure() execution
canScrollForward = true
)
remeasurement.forceRemeasure()
}
也許在即將發布的版本中,我們可以看到更新。
這是我制作粘性標題、列表和滾動的代碼
@ExperimentalFoundationApi
@Composable
private fun ListView(data: YourClass) {
//this is to remember state, internal API also use the same
val state = rememberLazyListState()
LazyColumn(Modifier.fillMaxSize(), state) {
itemsIndexed(items = data.list, itemContent = { index, dataItem ->
ItemView(dataItem)// your row
})
// header after some data, according to your condition
stickyHeader {
ItemDecoration()// compose fun for sticky header
}
// More items after header
itemsIndexed(items = data.list2, itemContent = { index, dataItem ->
ItemView(dataItem)// your row
})
}
// scroll to top
// I am scrolling to top every time data changes, use accordingly
CoroutineScope(Dispatchers.Main).launch {
state.snapToItemIndex(0, 0)
}
}
}
嘗試
lazyListState.animateScrollToItem(lazyListState.firstVisibleItemIndex)
@Composable
fun CircularScrollList(
value: Long,
onValueChange: () -> Unit = {}
) {
val lazyListState = rememberLazyListState()
val scope = rememberCoroutineScope()
val items = CircularAdapter(listOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
scope.launch { lazyListState.scrollToItem(items.midIndex()) }
LazyColumn(
modifier = Modifier
.requiredHeight(height = 120.dp)
.border(width = 1.dp, color = Color.Black),
state = lazyListState,
) {
items(items) {
if (!lazyListState.isScrollInProgress) {
scope.launch {
lazyListState.animateScrollToItem(lazyListState.firstVisibleItemIndex)
}
}
Text(
text = "$it",
modifier = Modifier.requiredHeight(40.dp),
style = TextStyle(fontSize = 30.sp)
)
}
}
}
class CircularAdapter(
private val content: List<Int>
) : List<Int> {
fun midIndex(): Int = Int.MAX_VALUE / 2 + 6
override val size: Int = Int.MAX_VALUE
override fun contains(element: Int): Boolean = content.contains(element = element)
override fun containsAll(elements: Collection<Int>): Boolean = content.containsAll(elements)
override fun get(index: Int): Int = content[index % content.size]
override fun indexOf(element: Int): Int = content.indexOf(element)
override fun isEmpty(): Boolean = content.isEmpty()
override fun iterator(): Iterator<Int> = content.iterator()
override fun lastIndexOf(element: Int): Int = content.lastIndexOf(element)
override fun listIterator(): ListIterator<Int> = content.listIterator()
override fun listIterator(index: Int): ListIterator<Int> = content.listIterator(index)
override fun subList(fromIndex: Int, toIndex: Int): List<Int> =
content.subList(fromIndex, toIndex)
}
我已經解決了2種方式
一種方式:我選擇了這種最好的方式
LaunchedEffect(true) {
repeat(Int.MAX_VALUE) {
delay(TIME_DELAY_BANNER)
pagerState.animateScrollToPage(page = it % pagerState.pageCount)
}
}
兩種方式:
var index = pagerState.currentPage
LaunchedEffect(true) {
while (true) {
delay(TIME_DELAY_BANNER)
if (index == pagerState.pageCount) {
index = 0
}
pagerState.animateScrollToPage(page = index++)
}
}
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