Android Composable 不会在单击按钮时重新组合

我有以下可组合的函数.这是一个简单的登录屏幕与用户名，密码和提交按钮.

当用户点击提交按钮时，如果用户名或密码字段为空，则会显示一个快捷栏.然而，它在第一次点击时起作用，但随后的点击不起作用.

如果需要显示快捷栏，我会认为按钮点击会强制合成内容重新组合，LaunchEffect键将为真.

@Composable
fun Login() {
    var username by remember { mutableStateOf("") }
    var password by remember { mutableStateOf("") }
    val scaffoldState = rememberScaffoldState()
    var shouldShowSnackBar by remember { mutableStateOf(false) }

    println("LoginScreen")

    LaunchedEffect(key1 = shouldShowSnackBar, block = {
        println("ShouldShowSnackBar")
        scaffoldState.snackbarHostState.showSnackbar(
            message = "Please enter a username and password",
            duration = SnackbarDuration.Short
        )
    })

   Scaffold(
        scaffoldState = scaffoldState
    ) {
        Column(modifier = Modifier.fillMaxWidth()) {
            OutlinedTextField(
                label = {
                    Text(text = "Username")
                },
                value = username,
                onValueChange = { newUsername ->
                    username = newUsername
                })

            OutlinedTextField(
                label = {
                    Text(text = "Password")
                },
                value = password,
                onValueChange = { newPassword ->
                    password = newPassword
                },
                visualTransformation = PasswordVisualTransformation())

            OutlinedButton(
                modifier = Modifier.fillMaxWidth(),
                onClick = {
                    shouldShowSnackBar = username.isEmpty() || password.isEmpty()
                    println("Button pressed: $shouldShowSnackBar")
                }) {
                Text(text = "Submit")
            }
        }
    }
}