在 LazyColumn 中将单个 AnimatedVisibility 设置为 true

Set a single AnimatedVisibility to true in a LazyColumn

我有一个用于操作系统信息的可组合函数,它会在单击时扩展详细信息,并在再次单击时还原。

@ExperimentalAnimationApi
@Composable
fun OSCard(os: OS) {
    var expanded by remember {
        mutableStateOf(false)
    }
    Column(modifier = Modifier
        .clickable { expanded = !expanded }
        .fillMaxWidth()) {
        Text(
            modifier = Modifier
                .padding(20.dp),
            text = os.name,
            style = MaterialTheme.typography.h6
        )
        AnimatedVisibility(visible = expanded) {
            Text(text = os.description, modifier = Modifier.padding(20.dp))
        }
        Divider(Modifier.height(2.dp))
    }
}

我创建了它的列表并通过 LazyColumn

传递了它
var OSs = listOf<OS>(
    OS(
        "Android",
        "Android is a mobile/desktop operating system..."
      ),
    OS(
        "Microsoft Windows",
        "Microsoft Windows, commonly referred to as Windows..."
      ),
    OS(
        "Linux",
        "Linux is a family of open-source Unix-like operating systems..."
      )
)

Surface(color = MaterialTheme.colors.background) {
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        items(items =  OSs){
            os -> OSCard(os)
        }
    }
}

虽然它按预期工作,但我想让它在打开一张卡并选择另一张卡时关闭之前打开的卡。

这是我想要避免的,有人可以告诉我如何做吗?

这是一种解决方案。向名为 isExpanded 的 OS 对象添加一个参数。只有当您单击卡片时,它才会设置为 true。单击处理程序将清除所有其他卡片中的标志。

我还添加了一个 id 参数,这样可以更轻松地找到被单击的项目。可以使用 name 参数。

状态变量 expandCard 需要读取才能触发重组,因此 var e = expandCard 用于读取值。另请注意,您的列表的创建必须在可组合项之外,否则它最终会被重新创建并且所有项目的 isExpanded 字段都将设置为 false。

最后,我不确定您为什么为此使用 LazyColumn。 LazyColumn 真正适用于大型数据集,主要用于分页。如果您有合理数量的项目,您可以只使用垂直滚动的普通列。

class MainActivity : ComponentActivity() {
    @ExperimentalAnimationApi
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        var OSs = listOf(
            OS(
                id = "android",
                name = "Android",
                description =  "Android is a mobile/desktop operating system..."
            ),
            OS(
                id = "mswindows",
                name = "Microsoft Windows",
                description = "Microsoft Windows, commonly referred to as Windows..."
            ),
            OS(
                id = "linux",
                name ="Linux",
                description = "Linux is a family of open-source Unix-like operating systems..."
            )
        )

        setContent {

            var expandCard by remember { mutableStateOf(false) }
            var e = expandCard

            Surface() {
                LazyColumn(  modifier = Modifier.fillMaxSize()) {
                    itemsIndexed(
                        items = OSs,
                        key = { index, os ->
                            os.name
                        }
                    ) { index, os ->
                        OSCard(os) {osClicked ->
                            val isExpanded = osClicked.isExpanded
                            OSs.forEach { it.isExpanded = false }
                            OSs.first { it.id == osClicked.id }.isExpanded = isExpanded
                            expandCard = !expandCard
                        }
                    }
                }
            }
        }
    }
}

@ExperimentalAnimationApi
@Composable
fun OSCard(
    os: OS,
    onClick: (os: OS) -> Unit
) {

    Column(modifier = Modifier
        .clickable {
            os.isExpanded = !os.isExpanded
            onClick(os)
        }
        .fillMaxWidth()) {
        Text(
            modifier = Modifier
                .padding(20.dp),
            text = os.name,
            style = MaterialTheme.typography.h6
        )

        AnimatedVisibility(visible = os.isExpanded) {
            Text(text = os.description, modifier = Modifier.padding(20.dp))
        }
        Divider(Modifier.height(2.dp))
    }
}

class OS(var id: String, var name: String, var description: String, var isExpanded: Boolean= false)