我需要在我的 SignScreen 的 onCreate 方法中呼叫一個函式，但沒有任何適用的地方。我無法currentUserCheck從任何地方呼叫函式。

我嘗試了什么：

1. init在 viewModel的塊中呼叫它。但問題是它扔nullPointerException在NavController這里。

2. 呼叫它，MainActivity但MyTheme我在這些范圍內遇到了許多奇怪的問題。

視圖模型：

@HiltViewModel                                                                                     
class SignViewModel (@ApplicationContext context: Context) : ViewModel() {
    val auth = FirebaseAuth.getInstance()

    init {
        currentUserCheck(NavController(context))
    }

    fun signIn(email: String?, password: String?, context: Context, navController: NavController) {

        if (email != null && email.isNotBlank() && password != null && password.isNotBlank()) {
            auth.signInWithEmailAndPassword(email, password).addOnSuccessListener {
                navController.navigate(ScreenHolder.ProfileScreen.route) {
                    popUpTo(ScreenHolder.SigningScreen.route) {
                        inclusive = true
                    }
                }
            }.addOnFailureListener {
                Toast.makeText(context, it.localizedMessage, Toast.LENGTH_LONG).show()
            }
        } else {

            Toast.makeText(
                context,
                "Lütfen email ve ?ifre alanlar?n? bo? b?rakmay?n?z.",
                Toast.LENGTH_LONG
            ).show()
        }
    }

    fun signUp(email: String?, password: String?, context: Context, navController: NavController) {
        if (email != null && email.isNotBlank() && password != null && password.isNotBlank()) {
            auth.createUserWithEmailAndPassword(email, password)
                .addOnSuccessListener {
                    navController.navigate(ScreenHolder.ProfileScreen.route) {
                        popUpTo(ScreenHolder.ProfileScreen.route) {
                            inclusive = true
                        }
                    }
                }
        } else {
            Toast.makeText(
                context,
                "Lütfen email ve ?ifre alanlar?n? bo? b?rakmay?n?z.",
                Toast.LENGTH_LONG
            ).show()
        }
    }

    fun currentUserCheck(navController: NavController) {
        if (auth.currentUser != null) {
            navController.navigate(ScreenHolder.ProfileScreen.route) {
                popUpTo(ScreenHolder.ProfileScreen.route) {
                    inclusive = true
                }
            }
        }
    }
}

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解決方案

正如@Pztar 所說，我將身份驗證控制操作宣告為 viewModel 中的一個狀態，然后我在我的 ComposableSignScreen中使用LaunchEffect觀察它并解決了它。

@HiltViewModel                                                                                     
class SignViewModel (@ApplicationContext context: Context) : ViewModel() {
    val auth = FirebaseAuth.getInstance()

    var currentUser = mutableStateOf(false)

    
//New currenUserCheck method that declare if state is true or not
fun currentUserCheck() {

        if (auth.currentUser != null) {
            currentUser.value = true

        }
    }
}

@Composable
fun SignScreen(viewModel: SignViewModel= hiltViewModel(),navController: NavController,context: Context) {

    //Observing the state from my composable and routing user if state is true.

    LaunchedEffect(key1 = Unit ){
        viewModel.currentUserCheck()
        if (viewModel.currentUser.value){
            navController.navigate(ScreenHolder.ProfileScreen.route) {
                popUpTo(ScreenHolder.SigningScreen.route) {
                    inclusive = true
                }
            }
        }
    }
}

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