Jetpack Compose

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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))
    }
}