Android 撰写小吃栏在配置更改时再次显示

Question

我想在android compose上显示一次snackbar，但是一旦我改变了屏幕旋转，snackbar就会再次显示，我从官方android文档中获取了这个例子，它正在做同样的事情：

@Composable
fun LoginScreen(
    state: Boolean = true,
    scaffoldState: ScaffoldState = rememberScaffoldState()
) {
    // If the UI state contains an error, show snackbar
    if (state) {

        // `LaunchedEffect` will cancel and re-launch if
        // `scaffoldState.snackbarHostState` changes
        LaunchedEffect(scaffoldState.snackbarHostState) {
            // Show snackbar using a coroutine, when the coroutine is cancelled the
            // snackbar will automatically dismiss. This coroutine will cancel whenever
            // `state.hasError` is false, and only start when `state.hasError` is true
            // (due to the above if-check), or if `scaffoldState.snackbarHostState` changes.
            scaffoldState.snackbarHostState.showSnackbar(
                message = "Error message",
                actionLabel = "Retry message"
            )
        }
    }

    Scaffold(scaffoldState = scaffoldState) {
    }
}

我的问题是：即使旋转发生变化，您如何显示一次带有副作用的小吃店？

Answer 1

例如，您可以使用rememberSaveable将状态保存到局部变量，并在小吃店消失时将其设置为false 。

var localState by rememberSaveable(state) { mutableStateOf(state) }
// If the UI state contains an error, show snackbar
if (localState) {

    // `LaunchedEffect` will cancel and re-launch if
    // `scaffoldState.snackbarHostState` changes
    LaunchedEffect(scaffoldState.snackbarHostState) {
        // Show snackbar using a coroutine, when the coroutine is cancelled the
        // snackbar will automatically dismiss. This coroutine will cancel whenever
        // `state.hasError` is false, and only start when `state.hasError` is true
        // (due to the above if-check), or if `scaffoldState.snackbarHostState` changes.
        scaffoldState.snackbarHostState.showSnackbar(
            message = "Error message",
            actionLabel = "Retry message"
        )
        localState = false
    }
}