CompositionLocal

//用于引发错误 放在全局
 var ActiveUser = compositionLocalOf<String> { error("No active user found!") }
//使用 中间组件不需要知道该CompositionLocal值，
 CompositionLocalProvider(ActiveUser provides "string") {
                SomeScreen()
            }
@Composable
fun SomeScreen() {
    User()
}
@Composable
fun User() {
    Text( ActiveUser.current , style = MaterialTheme.typography.body2)
}