使用Hilt与Navigation Component时返回导航出现空白屏问题

问题描述 #

我是一名Android开发新手，正在开发一个使用Hilt进行依赖注入、Navigation Component实现导航的项目。项目中有一个作为宿主的MainActivity，以及HomeFragment和DetailFragment两个碎片。从HomeFragment导航到DetailFragment的流程正常，但尝试返回或向上导航时，屏幕变为空白，没有任何碎片显示。

相关代码 #

MainActivity #

@AndroidEntryPoint
class MainActivity : BaseActivity<ActivityMainBinding, MainViewModel>() {
    @Inject
    lateinit var featuresNavigation: FeaturesNavigation

    private val viewModel: MainViewModel by viewModels()
    override fun getVM(): MainViewModel = viewModel

    private lateinit var startDestination: Pair<Int, NavArgument?>
    override val layoutId = R.layout.activity_main

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

        val navHostFragment =
            supportFragmentManager.findFragmentById(R.id.nav_host) as NavHostFragment
        featuresNavigation.bind(navHostFragment)

        with(intent) {
            initGraph(this)
            data = null
            replaceExtras(Bundle())
        }
    }

    private fun initGraph(intent: Intent?) {
        startDestination = createStartDestination(intent)

        if (startDestination.first == R.id.homeFragment) {
            Timber.e("MainAct test initGraph")
            featuresNavigation.setGraph(
                R.navigation.main_navigation,
                startDestination.first,
                startDestination.second
            )
        }
    }

    private fun createStartDestination(intent: Intent?): Pair<Int, NavArgument?> {
        val bundle = intent?.getBundleExtra(Constants.KeyParam.KEY_EXTRAS)

        return when (intent?.action) {

            else -> {
                R.id.homeFragment to null
            }
        }
    }
}

ActivityMain.xml #

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <FrameLayout
        android:id="@+id/layout_root"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/white">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/nav_host"
            android:name="com.usmh.libraries.navigationcomponent.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            tools:context=".ui.activity.MainActivity" />
    </FrameLayout>

</layout>

HomeFragment #

@AndroidEntryPoint
class HomeFragment :
    BaseFragment<FragmentHomeBinding, HomeViewModel>(R.layout.fragment_home) {

    @Inject
    lateinit var featuresNavigation: FeaturesNavigation

    private val viewModel: HomeViewModel by viewModels()
    override fun getVM() = viewModel


    override fun initView(savedInstanceState: Bundle?) {
        super.initView(savedInstanceState)
        activity?.window?.setBackgroundDrawable(null)

        featuresNavigation.openDetail()
    }
}

DetailFragment #

@AndroidEntryPoint
class DetailFragment :
    BaseFragment<FragmentDetailBinding, DetailViewModel>(R.layout.fragment_detail) {

    @Inject
    lateinit var featuresNavigation: FeaturesNavigation

    private val viewModel: DetailViewModel by viewModels()
    override fun getVM() = viewModel


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

        // TODO: Use the ViewModel
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return inflater.inflate(R.layout.fragment_detail, container, false)
    }

    override fun onBackPressed() {
        featuresNavigation.navigateUp()
    }
}

AppNavigatorImpl #

@ActivityScoped
class AppNavigatorImpl @Inject constructor() : BaseNavigatorImpl(), FeaturesNavigation {

    override fun openDetail(bundle: Bundle?) {
        openScreen(R.id.action_homeFragment_to_detailFragment, bundle, R.id.detailFragment)
    }
}

FeaturesNavigation #

interface FeaturesNavigation : BaseNavigator {
    fun openDetail(bundle: Bundle? = null)
}

main_navigation.xml #

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_navigation"
    app:startDestination="@id/homeFragment">

    <fragment
        android:id="@+id/homeFragment"
        android:name="com.usmh.features.ui.HomeFragment"
        android:label="HomeFragment"
        tools:layout="@layout/fragment_home">

        <action
            android:id="@+id/action_homeFragment_to_detailFragment"
            app:destination="@id/detailFragment" />
    </fragment>

    <fragment
        android:id="@+id/detailFragment"
        android:name="com.usmh.features.ui.DetailFragment"
        android:label="DetailFragment"
        tools:layout="@layout/fragment_detail" />
</navigation>

NavHostFragment #

public open class NavHostFragment : Fragment(), NavHost {
    private var navHostController: NavHostController? = null
    private var isPrimaryBeforeOnCreate: Boolean? = null
    private var viewParent: View? = null

    // State that will be saved and restored
    private var graphId = 0
    private var defaultNavHost = false

    final override val navController: NavController
        get() {
            checkNotNull(navHostController) { "NavController is not available before onCreate()" }
            return navHostController as NavHostController
        }

    @CallSuper
    public override fun onAttach(context: Context) {
        super.onAttach(context)

        if (defaultNavHost) {
            parentFragmentManager.beginTransaction()
                .setPrimaryNavigationFragment(this)
                .commit()
        }
</think_never_used_51bce0c785ca2f68081bfa7d91973934>