如何使用刀柄将 jetpack 组合中的“rememberNavController”注入到活动中？

Question

我正在尝试使用刀柄将我的navHostController 注入我的MainActivity。但是在尝试编译代码时出现以下错误：

> Task :app:kaptDebugKotlin
C:\Users\pierr\AndroidStudioProjects\AndroidApps\Compose\Udemy\course01\crud\app\build\generated\source\kapt\debug\com\example\crud\CrudApplication_HiltComponents.java:129: error: [Dagger/MissingBinding] androidx.navigation.NavHostController cannot be provided without an @Inject constructor or an @Provides-annotated method.
  public abstract static class SingletonC implements CrudApplication_GeneratedInjector,
                         ^
      androidx.navigation.NavHostController is injected at
          com.example.crud.ui.MainActivity.navHostController
      com.example.crud.ui.MainActivity is injected at
          com.example.crud.ui.MainActivity_GeneratedInjector.injectMainActivity(com.example.crud.ui.MainActivity) [com.example.crud.CrudApplication_HiltComponents.SingletonC ? com.example.crud.CrudApplication_HiltComponents.ActivityRetainedC ? com.example.crud.CrudApplication_HiltComponents.ActivityC]

> Task :app:kaptDebugKotlin FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:kaptDebugKotlin'.
> A failure occurred while executing org.jetbrains.kotlin.gradle.internal.KaptWithoutKotlincTask$KaptExecutionWorkAction
   > java.lang.reflect.InvocationTargetException (no error message)

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 8.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/7.0.2/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 5s
24 actionable tasks: 2 executed, 22 up-to-date

这是我的MainActivity 代码：

package com.example.crud.ui

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Surface
import androidx.navigation.NavHostController
import com.example.crud.navigation.NavigationComponent
import com.example.crud.ui.theme.CRUDTheme
import dagger.hilt.android.AndroidEntryPoint
import javax.inject.Inject

@AndroidEntryPoint
class MainActivity : ComponentActivity() {

    @Inject lateinit var navHostController: NavHostController

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            CRUDTheme {
                Surface(color = MaterialTheme.colors.background) {
                    NavigationComponent(navHostController)
                }
            }
        }
    }
}

这是我的NavigationModule 代码：

package com.example.crud.di

import androidx.compose.runtime.Composable
import androidx.navigation.compose.rememberNavController
import dagger.Module
import dagger.hilt.InstallIn
import dagger.hilt.android.components.ActivityComponent

@Module
@InstallIn(ActivityComponent::class)
object NavigationModule {
    @Composable
    fun provideNavHostController() = rememberNavController()
}

这是NavigationComponent 的代码（它以navHostController 作为参数，我试图注入MainActivity）：

package com.example.crud.navigation

import androidx.compose.runtime.Composable
import androidx.compose.runtime.livedata.observeAsState
import androidx.hilt.navigation.compose.hiltViewModel
import androidx.navigation.NavHostController
import androidx.navigation.NavType
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.navArgument
import com.example.crud.ui.screens.crud.details.DetailScreen
import com.example.crud.ui.screens.crud.register.RegisterScreen
import com.example.crud.ui.screens.home.HomeScreen
import com.example.crud.ui.screens.home.HomeViewModel

@Composable
fun NavigationComponent(navController: NavHostController) {
    NavHost(navController = navController, startDestination = Routes.HOME) {
        composable(Routes.HOME) {
            val homeViewModel: HomeViewModel = hiltViewModel()
            val cities = homeViewModel.cities.observeAsState(listOf())
            HomeScreen(
                cities = cities,
                navigateToDetailsAction = { navController.navigate(Routes.REGISTER) }
            ) { cityId ->
                navController.navigate(Routes.getDetailsDynamicRoute(cityId))
            }
        }
        composable(Routes.REGISTER) { RegisterScreen { navController.popBackStack() } }
        composable(
            route = Routes.DETAILS,
            arguments = listOf(navArgument(Routes.CITY_ID_KEY) { type = NavType.IntType })
        ) { backStackEntry ->
            val cityId = backStackEntry.arguments?.getInt(Routes.CITY_ID_KEY)
            cityId?.let {
                DetailScreen(cityId = it, popNavigation = { navController.popBackStack() })
            }
        }
    }
}

我认为这与解决问题无关，但Routes.kt文件中的代码如下：

package com.example.crud.navigation

object Routes {
    private const val DETAILS_BASE_ROUTE = "details/"
    const val HOME = "home"
    const val REGISTER = "register"
    const val CITY_ID_KEY = "cityId"
    const val DETAILS = "$DETAILS_BASE_ROUTE{$CITY_ID_KEY}"

    fun getDetailsDynamicRoute(cityId: Int) = "$DETAILS_BASE_ROUTE${cityId}"
}

我做错了什么？

Answer 1

您可以通过将NavHostController 包装在另一个类中来实现此行为。 将此 Navigator 类限定为您的 MainActivity（ActivityRetainedComponent 和 @ActivityRetainedScoped）并在记住它后设置 NavHostController。然后将其也注入您的ViewModels，您就可以从那里导航。

/**
 * Class to handle navigation. It should be injected into the screens' ViewModel
 */
class Navigator {

    private lateinit var navController: NavHostController

    fun setController(controller: NavHostController) {
        navController = controller
    }

    fun navigate() {
        // TODO handle navigation with the navController
    }
}

另外，记得注入一个由Navigator 实现的接口，这样你就可以创建一个MockNavigator 类来测试你的ViewModels。

Answer 2

但我认为你不需要在主类上创建 NavController，因为 la 类 NavigationComponent 的这一部分我认为这个类是负责处理这个类的。

我是 android 世界的新手，但 NavigationComponent 控制 NavController 及其与它的所有交互对我来说很有意义。

我一般都是这样用的

@Composable fun NavigationHost() {

val navController = rememberNavController()

MyTheme {
    NavHost(
        navController = navController,
        NavItem.Main.route
    )
    {

        composable(route = NavItem.Main.route) {
            FeedScreen { productOnClick ->
                navController.navigate(NavItem.Detail.createNavRoute(productOnClick.id))
            }
        }

        composable(route = NavItem.Main.route) {
            ConfirmationScreen {
                navController.navigate(NavItem.Main.route)
            }
        }
    }

}

}