Android Jetpack Compose 可滚动列表 LazyColumn

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Jetpack Compose

更多与Jetpack Compose相关的文章：
Android Jetpack Compose 沉浸式/透明状态栏 ProvideWindowInsets SystemUiController

前言

这是一个比较简单的知识点，但是在当前时间2021/08/03，在搜索引擎上还没能快速搜索到相关信息，所以贡献一下自己的了解。

LazyColumn

这个库来自androidx.compose.foundation.lazy

/*** The vertically scrolling list that only composes and lays out the currently visible items. The content block defines a DSL which allows you to emit items of different types. For example you can use LazyListScope.item to add a single item and LazyListScope.items to add a list of items.* Params:* 			modifier - the modifier to apply to this layout.* 			state - the state object to be used to control or observe the list's state.* 			contentPadding - a padding around the whole content. This will add padding for the. content after it has been clipped, which is not possible via modifier param. You can use it to add a padding before the first item or after the last one. If you want to add a spacing between each item use verticalArrangement.* 			reverseLayout - reverse the direction of scrolling and layout, when true items will be composed from the bottom to the top and LazyListState.firstVisibleItemIndex == 0 will mean we scrolled to the bottom.* 			verticalArrangement - The vertical arrangement of the layout's children. This allows to add a spacing between items and specify the arrangement of the items when we have not enough of them to fill the whole minimum size.* 			horizontalAlignment - the horizontal alignment applied to the items.* 			flingBehavior - logic describing fling behavior.* 			content - a block which describes the content. Inside this block you can use methods like LazyListScope.item to add a single item or LazyListScope.items to add a list of items.* Samples:* androidx.compose.foundation.samples.LazyColumnSample// Unresolved
*/
@Composable
fun LazyColumn(modifier: Modifier = Modifier,state: LazyListState = rememberLazyListState(),contentPadding: PaddingValues = PaddingValues(0.dp),reverseLayout: Boolean = false,verticalArrangement: Arrangement.Vertical =if (!reverseLayout) Arrangement.Top else Arrangement.Bottom,horizontalAlignment: Alignment.Horizontal = Alignment.Start,flingBehavior: FlingBehavior = ScrollableDefaults.flingBehavior(),content: LazyListScope.() -> Unit
) {LazyList(stateOfItemsProvider = rememberStateOfItemsProvider(content),modifier = modifier,state = state,contentPadding = contentPadding,flingBehavior = flingBehavior,horizontalAlignment = horizontalAlignment,verticalArrangement = verticalArrangement,isVertical = true,reverseLayout = reverseLayout)
}

从注解信息就能了解到这是一个支持纵向滚动的列表

使用方法

LazyColumn(// 列表反向显示//reverseLayout = true
) {// 显示列表items(list.size) { index ->val info = list[index]// 列表单项的UI}// 显示单个的UI，可以用作多个列表的分割，或者头部、底部之类的item {Text("这是底部", Modifier.padding(16.dp))}
}

同理，横向滚动就可以选择LazyRow

完事

下一篇应该会说 Android Jetpack Compose 的下拉刷新…

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