jetpackcompose碎片发行问题

Question

我需要在我的SignScreen的Oncreate方法中调用功能，但没有任何适用的位置。我无法从任何地方调用CurrentUserCheck函数。

我尝试过的内容：

1. 在init中调用它在ViewModel中。但是问题在于它扔了nullpoInterException navcontroller此处。

2. 在MainActivity和Mytheme中调用它，但我在这些范围中遇到了许多奇怪的问题。

ViewModel ：

@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 şifre alanlarını boş bırakmayınız.",
                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 şifre alanlarını boş bırakmayınız.",
                Toast.LENGTH_LONG
            ).show()
        }
    }

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

Answer 1

解决方案

正如@pztar所说，我在ViewModel中声明了控制操作为状态的身份验证，然后我在我的Composobable signscreen中使用 启动效果及已解决。

@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
                }
            }
        }
    }
}