Jetpack Compose——DropdownMenu（下拉菜单）的简单使用

基于compose_version=1.1.0-beta01版本 参数如下：

DropdownMenu(
    expanded: Boolean,//菜单栏状态
    onDismissRequest: () -> Unit,//菜单栏被关闭回调
    modifier: Modifier = Modifier,//布局修饰
    offset: DpOffset = DpOffset(0.dp, 0.dp),//要添加到菜单位置的偏移量 
    properties: PopupProperties = PopupProperties(focusable = true),//自定义的弹出框
    content: @Composable ColumnScope.() -> Unit//内容
)

简单使用：

@Composable
fun DropDownTest() {
    val context = LocalContext.current
    var expanded = remember {
        mutableStateOf(false)
    }
    val items = listOf("A", "B", "C", "D", "E")
    Box(
        Modifier
            .fillMaxSize()
            .padding(10.dp)
            .wrapContentSize(Alignment.TopStart)
    ) {
        TextButton(
            onClick = {
                expanded.value = true
            },
            modifier = Modifier.background(Color.LightGray)
        ) {
            Text(text = "下拉菜单")
        }

        DropdownMenu(expanded = expanded.value, onDismissRequest = { expanded.value = false }) {
            items.forEachIndexed { index, s ->
                DropdownMenuItem(onClick = {
                    expanded.value = false
                    Toast.makeText(context, s, Toast.LENGTH_SHORT).show()
                }) {
                    Text(text = s)
                }
            }
        }
    }
}

效果如图：