Jetpack Compose + Navigation - navigate() 上的无限循环

Question

我正在使用 Jetpack Compose + 导航（单个 Activity，无片段）并且我正在尝试执行如下导航路线：

SplashScreen ---（延迟）---> AuthScreen ---（如果成功）--> MainScreen

不幸的是，当我执行登录时，LoginScreen 可组合项中的函数 navigate() 导致无限循环。我不明白我是在触发重组还是发生了什么。不幸的是，很难共享所有代码，但请记住：

这个问题似乎与 LoginScreen 和 MainScreen 可组合项无关（您可以假设它们只是一个简单的 Text 可组合项）
它似乎也与 NavigationGraph 无关。事实上，如果我只是进行 SplashScreen --> MainScreen 转换，就不会出现问题
如果我删除行 navController.navigate("main") 就没有更多的循环；
代码基于（几乎是复制粘贴）this 示例

这是出现问题的 AuthScreen 代码。

@Composable
fun AuthScreen(navController: NavController) {
    val signInRequestCode = 1
    val context = LocalContext.current

    val mSignInViewModel: SignInGoogleViewModel = viewModel(
        factory = SignInGoogleViewModelFactory(context.applicationContext as Application)
    )

    val state = mSignInViewModel.googleUser.observeAsState()
    val user = state.value

    val isError = rememberSaveable { mutableStateOf(false) }


    val authResultLauncher =
        rememberLauncherForActivityResult(contract = GoogleApiContract()) { task ->
            try {
                val gsa = task?.getResult(ApiException::class.java)

                if (gsa != null) {
                    mSignInViewModel.fetchSignInUser(gsa.email, gsa.displayName)
                } else {
                    isError.value = true
                }
            } catch (e: ApiException) {
                Log.e("Authscreen", e.toString())
            }
        }

    AuthView(
        onClick = { authResultLauncher.launch(signInRequestCode) },
        isError = isError.value,
        mSignInViewModel
    )

    Log.d("TEST", "Loop check")  //THIS GOES LIKE CRAZY IN THE LOGCAT!

    user?.let {
        mSignInViewModel.hideLoading()

        //Create JSON adapter to move data
        val moshi = Moshi.Builder().build()
        val jsonAdapter = moshi.adapter(GoogleUserModel::class.java).lenient()
        val userJson = jsonAdapter.toJson(user)

        //Navigate to main screen
        navController.navigate("main")
    }

}

这是导航图代码：

const val ROOT_ROUTE = "root_route"

@Composable
fun SetupRootNavGraph(navController: NavHostController) {
    NavHost(
        navController = navController,
        startDestination = Screen.SplashScreen.route,
        route = ROOT_ROUTE
    ) {
        composable(Screen.SplashScreen.route) { SplashScreen(navController)}
        composable(Screen.AuthScreen.route) { AuthScreen(navController)}
        composable(Screen.MainScreen.route) {MainScreen(navController)}
    }
}

Answer 1

这是因为您正在尝试从可组合项进行导航。见 documentation

You should only call navigate() as part of a callback and not as part of your composable itself, to avoid calling navigate() on every recomposition.

例如您可以使用 LaunchEffect

Jetpack Compose + Navigation - navigate() 上的无限循环

Jetpack Compose + Navigation - Infinite loop on navigate()

android-jetpack-compose

infinite-loop

android-jetpack-navigation