当使用Fragment Factory和Navigation Component时，View没有设置NavController。

Question

我正在重构我的应用程序，使用碎片工厂。重构前导航组件一切正常，但现在碎片找不到导航控制器了，错误。

java.lang.IllegalStateException: View androidx.constraintlayout.widget.ConstraintLayout{7c24bdc V.E...... ......I. 0,0-1080,2088 #7f0a0061 app:id/auth_nav_host_fragment} does not have a NavController set
    at androidx.navigation.Navigation.findNavController(Navigation.java:84)
    at androidx.navigation.fragment.NavHostFragment.findNavController(NavHostFragment.java:118)
    at androidx.navigation.fragment.FragmentKt.findNavController(Fragment.kt:29)
    at com.kalianey.oneness.ui.auth.LauncherFragment.navLogin(LauncherFragment.kt:42)
    at com.kalianey.oneness.ui.auth.LauncherFragment.access$navLogin(LauncherFragment.kt:16)
    at com.kalianey.oneness.ui.auth.LauncherFragment$onViewCreated$1.onClick(LauncherFragment.kt:28)

我创建了一个碎片工厂。

@AuthScope
class AuthFragmentFactory
@Inject
constructor(
private val viewModelFactory: ViewModelProvider.Factory
) : FragmentFactory() {

override fun instantiate(classLoader: ClassLoader, className: String) =

    when (className) {

        OnboardingPagerFragment::class.java.name -> {
            OnboardingPagerFragment()
        }

        OnboardingOneFragment::class.java.name -> {
            OnboardingOneFragment()
        }

        OnboardingTwoFragment::class.java.name -> {
            OnboardingTwoFragment()
        }

        OnboardingThreeFragment::class.java.name -> {
            OnboardingThreeFragment()
        }

        LauncherFragment::class.java.name -> {
            LauncherFragment(viewModelFactory)
        }

        LoginFragment::class.java.name -> {
            LoginFragment(viewModelFactory)
        }

        RegisterFragment::class.java.name -> {
            RegisterFragment(viewModelFactory)
        }

        ForgotPasswordFragment::class.java.name -> {
            ForgotPasswordFragment(viewModelFactory)
        }

        else -> {
            LauncherFragment(viewModelFactory)
        }
    }

 }

在我的模块中，我创建了一个碎片工厂： Provided like this in my module:

@JvmStatic
@AuthScope
@Provides
fun provideFragmentFactory(viewModelFactory: ViewModelProvider.Factory, requestManager: RequestManager, sessionManager: SessionManager): FragmentFactory{
    return AuthFragmentFactory(viewModelFactory)
}

我在我的AuthActivity中也是这样设置的。

override fun onCreate(savedInstanceState: Bundle?) {
    inject()
    supportFragmentManager.fragmentFactory = fragmentFactory
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_auth)
}

我到底做错了什么？

Answer 1

当你设置一个 FragmentFactory，它负责实例化 每一 碎片 AuthActivity 可能需要。 然而，当系统试图实例化的是 NavHostFragment你的工厂创建了一个 LauncherFragment 而不是。 这意味着你从未真正创建过一个 NavHostFragment，你没有一个 NavController.

而不是创建一个 LauncherFragment，你的 else 的情况下，应该创建任何一个被请求的片段类。

else -> {
    super.instantiate(classLoader, className)
}