NavHostFragment在onDestroyView中崩溃

如何解决NavHostFragment在onDestroyView中崩溃

我有一个Activity应用，其中有一个FragmentContainerView和一个BottomNavigationView设置：

<?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">

    <LinearLayout
        android:id="@+id/layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            app:defaultNavHost="true"
            app:navGraph="@navigation/splash" />

        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/bottom_navigation"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@android:color/white"
            android:visibility="gone"
            app:elevation="12dp"
            app:labelVisibilityMode="unlabeled"
            app:menu="@menu/menu_bottom_nav_main" />
    </LinearLayout>
</layout>

当用户进入应用程序时，我需要显示一个初始页面（如果需要，可以启动），然后将其导航到主页。因此，我创建了4个导航图，其中1个用于启动画面，3个用于底部导航。我正在使用Android示例中的this灭绝技术，通过3个图表来设置底部导航。这是我的MainActivity代码：

@AndroidEntryPoint
class MainActivity : BaseActivity<ActivityMainBinding,Mainviewmodel>(
    R.layout.activity_main,Mainviewmodel::class,) {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        if (!vm.splashPassed) {
            val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
            currentNavController = mutablelivedata(navHostFragment.navController)
        } else if (savedInstanceState == null && vm.splashPassed) {
            naviagatetoHome()
        }
    }

    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
        super.onRestoreInstanceState(savedInstanceState)
        if (vm.splashPassed) {
            naviagatetoHome()
        }
    }

    fun naviagatetoHome() {
        vm.splashPassed = true
        val fragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
        supportFragmentManager.beginTransaction()
            .remove(fragment)
            .commitNow()

        setupBottomNavigationBar()
    }

    private lateinit var currentNavController: LiveData<NavController>

    private fun setupBottomNavigationBar() {
        binding.bottomNavigation.isVisible = true
        val navGraphIds = arraylistof(R.navigation.explore,R.navigation.plan,R.navigation.profile)

        // Setup the bottom navigation view with a list of navigation graphs
        currentNavController = binding.bottomNavigation.setupWithNavController(
            navGraphIds = navGraphIds,fragmentManager = supportFragmentManager,containerId = R.id.nav_host_fragment,intent = intent,)
    }

    override fun onBackpressed() {
        val navController = currentNavController.value ?: return super.onBackpressed()

        if (navController.graph.id == R.id.splash) return super.onBackpressed()

        val destination = navController.currentDestination?.id
        val rootDestinations = listof(R.id.planFragment,R.id.profileFragment,R.id.exploreFragment,R.id.panelFragment)
        if (destination !in rootDestinations && navController.navigateUp()) return

        super.onBackpressed()
    }
}

这就是我从naviagatetoHome呼叫SplashFragment的方式：

vm.navigateHome.observe(viewLifecycleOwner) {
    (requireActivity() as? MainActivity)?.naviagatetoHome()
}

一切正常，直到Activity执行onDestroy（被推到后台时）为止，并且崩溃并带有以下堆栈跟踪：

2020-09-13 13：17：38.064 28092-28092 / com.abc.dev E / AndroidRuntime：致命异常：主要流程：com.abc.dev，PID：28092 java.lang.RuntimeException：无法销毁活动{com.abc.dev/com.abc.ui.activity.MainActivity}： java.lang.IllegalStateException：视图 androidx.fragment.app.FragmentContainerView {e7a7304 V.E ...... ...... ID 0,0-1080,1868＃7f0a026a app：id / nav_host_fragment}没有导航控制器集在android.app.ActivityThread.performDestroyActivity（ActivityThread.java:4941）在android.app.ActivityThread.handleDestroyActivity（ActivityThread.java:4970）在android.app.servertransaction.DestroyActivityItem.execute（DestroyActivityItem.java:44）在android.app.servertransaction.TransactionExecutor.executeLifecycleState（TransactionExecutor.java:176）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:97）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:2016）在android.os.Handler.dispatchMessage（Handler.java:107）在android.os.Looper.loop（Looper.java:214）在android.app.ActivityThread.main（ActivityThread.java:7356）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:492）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:930）造成原因：java.lang.IllegalStateException：查看androidx.fragment.app.FragmentContainerView {e7a7304 V.E ...... ...... ID 0,1868＃7f0a026a app：id / nav_host_fragment}没有导航控制器集在androidx.navigation.Navigation.findNavController（Navigation.java:84）在androidx.navigation.fragment.NavHostFragment.onDestroyView（NavHostFragment.java:388）在androidx.fragment.app.Fragment.performDestroyView（Fragment.java:3171）在androidx.fragment.app.FragmentStateManager.destroyFragmentView（FragmentStateManager.java:726）在androidx.fragment.app.FragmentStateManager.movetoExpectedState（FragmentStateManager.java:360）在androidx.fragment.app.FragmentStore.movetoExpectedState（FragmentStore.java:112）在androidx.fragment.app.FragmentManager.movetoState（FragmentManager.java:1632）在androidx.fragment.app.FragmentManager.dispatchStateChange（FragmentManager.java:3109）在androidx.fragment.app.FragmentManager.dispatchDestroy（FragmentManager.java:3088）在androidx.fragment.app.FragmentController.dispatchDestroy（FragmentController.java:334）在androidx.fragment.app.FragmentActivity.onDestroy（FragmentActivity.java:322）在androidx.appcompat.app.AppCompatActivity.onDestroy（AppCompatActivity.java:278）在android.app.Activity.performDestroy（Activity.java:8048）在android.app.Instrumentation.callActivityOnDestroy（Instrumentation.java:1334）在android.app.ActivityThread.performDestroyActivity（ActivityThread.java:4926）在android.app.ActivityThread.handleDestroyActivity（ActivityThread.java:4970）在android.app.servertransaction.DestroyActivityItem.execute（DestroyActivityItem.java:44）在android.app.servertransaction.TransactionExecutor.executeLifecycleState（TransactionExecutor.java:176）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:97）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:2016）在android.os.Handler.dispatchMessage（Handler.java:107）在android.os.Looper.loop（Looper.java:214）在android.app.ActivityThread.main（ActivityThread.java:7356）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:492）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:930）

花了一些时间进行调试后，我意识到androidx.navigation.fragment.NavHostFragment.onDestroyView尝试使用Navigation.findNavController方法，该方法存在一些here描述的问题。我还在android / architecture-components-samples GitHub存储库中找到了一个 pull request，它没有提供任何明确的解决方案。

注释： 如果我通过调用onCreate在setupBottomNavigationBar中设置了底部导航，则不会收到错误消息，一切都会顺利进行。

我坚持了一个多星期，不知道如何解决。

tnx，阅读了我的长问。

更新1： 我已经注意到，如果我至少一次更改了所选的底部导航项，则不会发生崩溃。

如果我想在分离前一个NavHostFragment时添加自定义动画，如下所示，则始终出现相同的错误：

fun naviagatetoHome() {
    vm.splashPassed = true
    val fragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
    supportFragmentManager.beginTransaction()
        .setCustomAnimations(R.anim.nav_default_enter_anim,R.anim.nav_default_exit_anim)
        .remove(fragment)
        .commitNow()

    setupBottomNavigationBar()
}

2020-09-14 00：18：37.705 3434-3434 / com.abc.dev E / AndroidRuntime：FATAL 例外：主要流程：com.abc.dev，PID：3434 java.lang.IllegalStateException：查看androidx.fragment.app.FragmentContainerView {1414b18 V.E ...... ...... ID 0,1868＃7f0a026a app：id / nav_host_fragment}没有导航控制器集在androidx.navigation.Navigation.findNavController（Navigation.java:84）在androidx.navigation.fragment.NavHostFragment.onDestroyView（NavHostFragment.java:388）在androidx.fragment.app.Fragment.performDestroyView（Fragment.java:3171）在androidx.fragment.app.FragmentStateManager.destroyFragmentView（FragmentStateManager.java:726）在androidx.fragment.app.FragmentStateManager.movetoExpectedState（FragmentStateManager.java:360）在androidx.fragment.app.SpecialEffectsController $ FragmentStateManagerOperation.complete（SpecialEffectsController.java:512）在androidx.fragment.app.DefaultSpecialEffectsController.removeCancellationSignal（DefaultSpecialEffectsController.java:81）在androidx.fragment.app.DefaultSpecialEffectsController $ 4 $ 1.run（DefaultSpecialEffectsController.java:255）在android.os.Handler.handleCallback（Handler.java:883）在android.os.Handler.dispatchMessage（Handler.java:100）在android.os.Looper.loop（Looper.java:214）在android.app.ActivityThread.main（ActivityThread.java:7356）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:492）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:930）

解决方法

这是导航示例中代码的一部分，该代码确定要附加和分离其他片段的片段。

    // Attach or detach nav host fragment depending on whether it's the selected item.
    if (this.selectedItemId == graphId) {
        selectedNavController.value = navHostFragment.navController
            attachNavHostFragment(fragmentManager,navHostFragment,index == 0)
    } else {
        detachNavHostFragment(fragmentManager,navHostFragment)
    }

这是怎么回事？
attach ：将NavHostFragment与容器附加在一起时， onViewCreated会被调用，它还会为父视图（即FragmentContainerView）设置NavController。

分离：调用NavHostFragment从容器onDestroyView分离时。 onDestroyView将父视图的NavController设置为null。

attach仅针对selectedFragmentId被调用，所有其他片段都被分离。

以下是您的日志记录，将第一个片段视为选定片段：

2020-09-14 09:34:58.602 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onDestroyView
2020-09-14 09:34:58.602 12023-12023/com.beetlestance.testingnavigation D/navController: SplashFragment removing navController from parent
2020-09-14 09:34:58.611 12023-12023/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 1
2020-09-14 09:34:58.616 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 09:34:58.620 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onViewCreated
2020-09-14 09:34:58.620 12023-12023/com.beetlestance.testingnavigation D/navController: FirstBottomFragment setting navController to parent
2020-09-14 09:34:58.633 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onResume
2020-09-14 09:34:58.634 12023-12023/com.beetlestance.testingnavigation D/bottomsheet: attach 1
2020-09-14 09:34:58.635 12023-12023/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 2
2020-09-14 09:34:58.640 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 09:34:58.643 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onViewCreated
2020-09-14 09:34:58.643 12023-12023/com.beetlestance.testingnavigation D/navController: SecondBottomFragment setting navController to parent
2020-09-14 09:34:58.654 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onResume
2020-09-14 09:34:58.656 12023-12023/com.beetlestance.testingnavigation D/bottomsheet: detach 2
2020-09-14 09:34:58.660 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onDestroyView
2020-09-14 09:34:58.660 12023-12023/com.beetlestance.testingnavigation D/navController: SecondBottomFragment removing navController from parent
2020-09-14 09:34:58.661 12023-12023/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 3
2020-09-14 09:34:58.666 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 09:34:58.668 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onViewCreated
2020-09-14 09:34:58.668 12023-12023/com.beetlestance.testingnavigation D/navController: ThirdBottomFragment setting navController to parent
2020-09-14 09:34:58.678 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onResume
2020-09-14 09:34:58.680 12023-12023/com.beetlestance.testingnavigation D/bottomsheet: detach 3
2020-09-14 09:34:58.684 12023-12023/com.beetlestance.testingnavigation D/navHostLifecycle: onDestroyView
2020-09-14 09:34:58.684 12023-12023/com.beetlestance.testingnavigation D/navController: ThirdBottomFragment removing navController from parent

从日志中很明显，分离是最后一个调用而不是附加，这将导致父级NavController为空。

解决方案： 最后应附加选定的片段，这将在此处解决问题。如果默认情况下您为底部导航选择了不同的ID，则可以仅将片段附加到forEach循环之外，而不必反转列表。

另一种方法是将您的底页贴在片段内，这将简化大多数情况。飞溅片段将始终是导航到您的底部导航容器片段的起始目的地，该片段将在onViewCreated中设置底部工作表。选中https://github.com/beetlestance/android-extensions

在onCreate中进行设置为什么会起作用？

仅在至少开始活动时才附加或分离片段。因此，当您在onCreate中设置底部导航时，NavHostFragment的生命周期会有所不同。

在onCreate中设置了底部导航的情况下的日志：

2020-09-14 10:07:17.659 15260-15260/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 1
2020-09-14 10:07:18.011 15260-15260/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 10:07:18.017 15260-15260/com.beetlestance.testingnavigation D/bottomsheet: attach 1
2020-09-14 10:07:18.041 15260-15260/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 2
2020-09-14 10:07:18.069 15260-15260/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 10:07:18.073 15260-15260/com.beetlestance.testingnavigation D/bottomsheet: detach 2
2020-09-14 10:07:18.077 15260-15260/com.beetlestance.testingnavigation D/bottomSheet: obtain navHostFragment 3
2020-09-14 10:07:18.098 15260-15260/com.beetlestance.testingnavigation D/navHostLifecycle: onCreate
2020-09-14 10:07:18.108 15260-15260/com.beetlestance.testingnavigation D/bottomsheet: detach 3
2020-09-14 10:07:18.173 15260-15260/com.beetlestance.testingnavigation D/mainActivityLifecycle: onStart
2020-09-14 10:07:18.208 15260-15260/com.beetlestance.testingnavigation D/navHostLifecycle: onViewCreated
2020-09-14 10:07:18.208 15260-15260/com.beetlestance.testingnavigation D/navController: FirstBottomFragment setting navController to parent
2020-09-14 10:07:18.292 15260-15260/com.beetlestance.testingnavigation D/mainActivityLifecycle: onResume
2020-09-14 10:07:18.304 15260-15260/com.beetlestance.testingnavigation D/navHostLifecycle: onResume

您可以检查onDestroyView是否未调用NavHostFragment。因此NavController已正确设置。

希望这会有所帮助。

问题是在最后调用detach而不是attach时引起的，这会迫使navController在父级NavHostFragment上为null。

NavHostFragment在onDestroyView中崩溃

如何解决NavHostFragment在onDestroyView中崩溃

解决方法

相关推荐