android - 多个异常 : Unable to start activity, Unable to instantiate fragment, Error inflating class

Question

我是 Kotlin 的新手，我正在学习教程。运行我的应用程序会导致它在运行时崩溃。我在底部导航栏应用程序中有三个 fragment 和一个主要 Activity 。我的目标实际上只是成功运行该应用程序，以便我可以尝试 Room 数据库、数据绑定(bind)和此类概念。我搜索了它对我不起作用但没有运气的可能原因。这是当前的完整错误消息:

    2021-02-27 14:58:23.967 23883-23883/com.jwanhsulaiman.talktag E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.jwanhsulaiman.talktag, PID: 23883
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jwanhsulaiman.talktag/com.jwanhsulaiman.talktag.MainActivity}: android.view.InflateException: Binary XML file line #21: Binary XML file line #21: Error inflating class androidx.fragment.app.FragmentContainerView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2919)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3054)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1814)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:280)
        at android.app.ActivityThread.main(ActivityThread.java:6706)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: android.view.InflateException: Binary XML file line #21: Binary XML file line #21: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: android.view.InflateException: Binary XML file line #21: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.jwanhsulaiman.talktag.ui.home.HomeFragment: could not find Fragment constructor
        at androidx.fragment.app.Fragment.instantiate(Fragment.java:625)
        at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57)
        at androidx.fragment.app.FragmentManager$3.instantiate(FragmentManager.java:483)
        at androidx.navigation.fragment.FragmentNavigator.instantiateFragment(FragmentNavigator.java:132)
        at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:162)
        at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:58)
        at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:71)
        at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:28)
        at androidx.navigation.NavController.navigate(NavController.java:1059)
        at androidx.navigation.NavController.onGraphCreated(NavController.java:639)
        at androidx.navigation.NavController.setGraph(NavController.java:592)
        at androidx.navigation.NavController.setGraph(NavController.java:557)
        at androidx.navigation.NavController.setGraph(NavController.java:539)
        at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:248)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:2936)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:472)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2177)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2094)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1959)
        at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:311)
        at androidx.fragment.app.FragmentContainerView.<init>(FragmentContainerView.java:176)
        at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:52)
        at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
        at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:313)
        at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:292)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:780)
2021-02-27 14:58:23.971 23883-23883/com.jwanhsulaiman.talktag E/AndroidRuntime:     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:696)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:170)
        at com.jwanhsulaiman.talktag.MainActivity.onCreate(MainActivity.kt:15)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2899)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3054)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1814)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:280)
        at android.app.ActivityThread.main(ActivityThread.java:6706)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NoSuchMethodException: <init> []
        at java.lang.Class.getConstructor0(Class.java:2327)
        at java.lang.Class.getConstructor(Class.java:1725)
        at androidx.fragment.app.Fragment.instantiate(Fragment.java:610)
            ... 50 more

我尝试将第 21 行的 XML 文件(根据错误)从 fragment 更改为 androidx.fragment.app.FragmentContainerView(根据 Android Studio 的建议用鼠标悬停时。我尝试添加依赖项，但似乎没有任何改变。我将提供我的代码的样子。

MainActivity.kt(错误说它在 setContentView(R.layout.activity_main) 上崩溃)

package com.jwanhsulaiman.talktag

import android.os.Bundle
import com.google.android.material.bottomnavigation.BottomNavigationView
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val navView: BottomNavigationView = findViewById(R.id.nav_view)

        val navController = findNavController(R.id.nav_host_fragment)
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        val appBarConfiguration = AppBarConfiguration(setOf(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications))
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    }
}

activity_main.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
<androidx.constraintlayout.widget.ConstraintLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_nav_menu" />

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        class = "androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@id/nav_view"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/mobile_navigation" />

</androidx.constraintlayout.widget.ConstraintLayout>
</layout>

以及 HomeFragment 的完整 fragment ，以防相关

    package com.jwanhsulaiman.talktag.ui.home

import android.content.Context
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProvider
import com.jwanhsulaiman.talktag.R
import com.jwanhsulaiman.talktag.database.VocabData
import com.jwanhsulaiman.talktag.database.VocabRepository
import com.jwanhsulaiman.talktag.databinding.FragmentHomeBinding

class HomeFragment(val applicationContext: Context) : Fragment() {

    private lateinit var homeViewModel: HomeViewModel
    private lateinit var binding: FragmentHomeBinding

    override fun onCreateView(
            inflater: LayoutInflater,
            container: ViewGroup?,
            savedInstanceState: Bundle?
    ): View? {
        homeViewModel =
                ViewModelProvider(this).get(HomeViewModel::class.java)
        val root = inflater.inflate(R.layout.fragment_home, container, false)
        val textView: TextView = root.findViewById(R.id.text_home)
        homeViewModel.text.observe(viewLifecycleOwner, Observer {
            textView.text = it
        })

        binding = DataBindingUtil.inflate(inflater, R.layout.fragment_home, container, false)
        val dao = VocabData.getInstance(this).VocabDao
        val repository = VocabRepository(dao)
        val factory = HomeViewModelFactory(repository)
        homeViewModel = ViewModelProvider(this, factory).get(HomeViewModel::class.java)
        binding.myViewModel = homeViewModel
        binding.lifecycleOwner = this
        displayVocabList()

        return binding.root
    }

    private fun displayVocabList() {
    homeViewModel.vocabs.observe(viewLifecycleOwner, Observer {
        Log.i("MYTAG", it.toString())
    })

    }
}

感谢您的任何见解!

Answer 1

Caused by: java.lang.NoSuchMethodException: <init> []

从 HomeFragment 中移除构造函数，原因有二:

1. 它不会工作，因为 fragment 系统需要一个公共(public)的零参数构造函数

2. 您不需要传入 Context，因为一旦您的 fragment 附加到 Activity ，您就可以调用 requireContext() 来检索 Context 来使用(如果你确实需要 Application，可以引用 applicationContext)