Android MVVM Todo应用启动报错：无法实例化HomeFragment

API 探路者

2026-8-18

问题：Fragment实例化失败引发InflateException错误

我正在开发一款基于MVVM架构的Todo应用，包含两个Fragment：用户可在AddNoteFragment中输入笔记，笔记会在HomeFragment的RecyclerView中展示。已将HomeFragment设置为导航组件的起始目标，但编写完RecyclerView Adapter后，应用启动时出现android.view.InflateException错误，完整错误信息显示无法实例化HomeFragment，找不到无参构造函数。

相关代码

<?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/navigation"
    app:startDestination="@id/homeFragment">

    <fragment
        android:id="@+id/homeFragment"
        android:name="com.enestigli.todoapp.presentation.home.home.HomeFragment"
        android:label="fragment_home"
        tools:layout="@layout/fragment_home" >
        <action
            android:id="@+id/action_homeFragment_to_addNoteFragment"
            app:destination="@id/addNoteFragment" />
    </fragment>
    <fragment
        android:id="@+id/addNoteFragment"
        android:name="com.enestigli.todoapp.presentation.home.addnote.AddNoteFragment"
        android:label="fragment_add_note"
        tools:layout="@layout/fragment_add_note" >
        <action
            android:id="@+id/action_addNoteFragment_to_homeFragment"
            app:destination="@id/homeFragment" />
    </fragment>
</navigation>

HomeFragment

@AndroidEntryPoint
class HomeFragment @Inject constructor(
    private val homeRecyclerAdapter:HomeRecyclerAdapter
): Fragment(R.layout.fragment_home) {

    private lateinit var viewModel: HomeViewModel
    private var fragmentBinding : FragmentHomeBinding? = null

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProvider(requireActivity()).get(HomeViewModel::class.java)

        val binding = FragmentHomeBinding.bind(view)
        fragmentBinding = binding

        subscribeToObservers()

        binding.HomeFragmentRecyclerView.adapter = homeRecyclerAdapter
        binding.HomeFragmentRecyclerView.layoutManager = LinearLayoutManager(requireContext())


        binding.fab.setOnClickListener{
            findNavController().navigate(HomeFragmentDirections.actionHomeFragmentToAddNoteFragment())
        }


    }

    private fun subscribeToObservers(){
        viewModel.noteList.observe(viewLifecycleOwner, Observer {
            homeRecyclerAdapter.noteList = it
        })
    }


    override fun onDestroy() {
        fragmentBinding = null
        super.onDestroy()

    }

}

HomeViewModel

@HiltViewModel
class HomeViewModel @Inject constructor(
    private val repository: INoteRepository
): ViewModel() {

    val noteList = repository.getNote()

}

HomeRecyclerAdapter

class HomeRecyclerAdapter : RecyclerView.Adapter<HomeRecyclerAdapter.HomeViewHolder>(){


    private val diffUtil = object : DiffUtil.ItemCallback<Note>(){

      
        override fun areItemsTheSame(oldItem: Note, newItem: Note): Boolean {
            return oldItem == newItem
        }

        override fun areContentsTheSame(oldItem: Note, newItem: Note): Boolean {
            return oldItem == newItem
        }

     
    }

    //DiffUtil helper
    private val recyclerListDiffer = AsyncListDiffer(this,diffUtil)


    var noteList :List<Note>
        get() = recyclerListDiffer.currentList
        set(value) = recyclerListDiffer.submitList(value)



    class HomeViewHolder(itemView: View):RecyclerView.ViewHolder(itemView)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): HomeViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.home_row,parent,false)
        return HomeViewHolder(view)
    }

    override fun onBindViewHolder(holder: HomeViewHolder, position: Int) {

        val title = holder.itemView.findViewById<TextView>(R.id.AddNoteFragmentTxtTitle)
        val desc =  holder.itemView.findViewById<TextView>(R.id.AddNoteFragmentTxtNote)
        val priority = holder.itemView.findViewById<TextView>(R.id.AddNoteFragmentRadioGroup)

        val note = noteList[position]

        holder.itemView.apply {
            title?.text = "Title: ${note.title}"
        }


    }

    override fun getItemCount(): Int {
       return noteList.size
    }
}

完整错误栈

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.enestigli.todoapp, PID: 6741
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.enestigli.todoapp/com.enestigli.todoapp.presentation.home.main.MainActivity}: android.view.InflateException: Binary XML file line #10 in com.enestigli.todoapp:layout/activity_main: Binary XML file line #10 in com.enestigli.todoapp:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3676)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3813)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2308)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7898)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
     Caused by: android.view.InflateException: Binary XML file line #10 in com.enestigli.todoapp:layout/activity_main: Binary XML file line #10 in com.enestigli.todoapp:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: android.view.InflateException: Binary XML file line #10 in com.enestigli.todoapp:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.enestigli.todoapp.presentation.home.home.HomeFragment: could not find Fragment constructor
        at androidx.fragment.app.Fragment.instantiate(Fragment.java:678)
        at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57)
        at androidx.fragment.app.FragmentManager$3.instantiate(FragmentManager.java:498)
        at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:190)
        at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:162)
        at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.kt:83)
        at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.kt:49)
        at androidx.navigation.NavController.navigateInternal(NavController.kt:260)
        at androidx.navigation.NavController.navigate(NavController.kt:1719)
        at androidx.navigation.NavController.onGraphCreated(NavController.kt:1161)
        at androidx.navigation.NavController.setGraph(NavController.kt:1086)
        at androidx.navigation.NavController.setGraph(NavController.kt:1039)
        at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.kt:155)
        at androidx.fragment.app.Fragment.performCreate(Fragment.java:3090)
        at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:257)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1890)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1814)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1720)
        at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:323)
        at androidx.fragment.app.FragmentContainerView.<init>(FragmentContainerView.kt:158)
        at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:53)
        at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:136)
        at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:248)
E/AndroidRuntime:     at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:227)
        at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1073)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1001)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:965)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1127)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1088)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:686)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:538)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:485)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:710)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
        at com.enestigli.todoapp.presentation.home.main.MainActivity.onCreate(MainActivity.kt:17)
        at android.app.Activity.performCreate(Activity.java:8290)
        at android.app.Activity.performCreate(Activity.java:8269)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1384)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3657)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3813)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2308)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7898)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
     Caused by: java.lang.NoSuchMethodException: com.enestigli.todoapp.presentation.home.home.HomeFragment.<init> []
        at java.lang.Class.getConstructor0(Class.java:2363)
        at java.lang.Class.getConstructor(Class.java:1759)
        at androidx.fragment.app.Fragment.instantiate(Fragment.java:663)
            ... 51 more

问题根源

HomeFragment使用带参数的@Inject构造函数，但Android系统实例化Fragment必须要有无参构造函数，导致实例化失败进而引发InflateException。

解决方案

将HomeRecyclerAdapter改为字段注入，移除带参数的构造函数，修改后的HomeFragment代码如下：

@AndroidEntryPoint
class HomeFragment : Fragment(R.layout.fragment_home) {
    @Inject
    lateinit var homeRecyclerAdapter: HomeRecyclerAdapter
    // 其他代码不变
}

内容的提问来源于stack exchange，提问作者NewPartizal

Android MVVM Todo应用启动报错：无法实例化HomeFragment

相关代码 #

navigation.xml #

HomeFragment #

HomeViewModel #

HomeRecyclerAdapter #

完整错误栈 #

问题根源 #

解决方案 #