如何从 Scroll from Android Compose 获取滚动的百分比或总数？

Question

我需要使用 Android Compose with states provided from ScrollState or NestedScrollState 在任何屏幕上获取屏幕上滚动总数的百分比，如何获取此信息？

Answer 1

您可以从 ScrollState class 的 value 和 maxValue 字段中获取。

@Composable
fun ScrollTestWithColumn() {
    val formatter = remember { DecimalFormat("0.0")} // optional
    val scrollState = rememberScrollState()
    val percent = (scrollState.value.toFloat() / scrollState.maxValue.toFloat()) * 100f
    val scrollText = "scroll: ${formatter.format(percent)}"
    Box {
        Column(
            Modifier
                .fillMaxSize()
                .verticalScroll(scrollState)
        ) {
            repeat(200) {
                Text(text = "Item $it", Modifier.padding(16.dp))
            }
        }
        Text(text = scrollText, Modifier.align(Alignment.BottomEnd))
    }
}

如果您需要使用 LazyColumn 实现此逻辑，我认为您可以基于可见索引来实现，因为项目是延迟加载的。

@Composable
fun ScrollTestWithLazyColumn() {
    val formatter = remember { DecimalFormat("0.0") }
    val scrollState = rememberLazyListState()
    val totalItemsCount = 200
    val firstVisibleIndex = scrollState.firstVisibleItemIndex
    val visibleItemsCount = scrollState.layoutInfo.visibleItemsInfo.size
    val percent = (firstVisibleIndex / (totalItemsCount - visibleItemsCount).toFloat()) * 100f
    val scrollText = "scroll: ${formatter.format(percent)}"
    Box {
        LazyColumn(
            state = scrollState,
            modifier = Modifier.fillMaxSize()
        ) {
            items(totalItemsCount) {
                Text(text = "Item $it", Modifier.padding(16.dp))
            }
        }
        Text(text = scrollText, Modifier.align(Alignment.BottomEnd))
    }
}

如何从 Scroll from Android Compose 获取滚动的百分比或总数？

How get the percentage or total scrolled from Scroll from Android Compose?

android

android-jetpack-compose