我的应用程序不断崩溃并出现致命异常

Question

我正在开发 pluralsight 的 android note keeper 应用程序，我遇到了两个问题：第一个是该活动旨在使用 ListView 显示笔记列表，但没有显示。其次，我有一个浮动操作按钮，应该允许我创建一个新的笔记，但是当我点击它时，应用程序崩溃了。我正在使用 genymotion 模拟器来运行应用程序。

我发现我的 nav_graph 中没有 NavHostFragment，但我已经实现了它，但它仍然无法正常工作 这是错误信息。

   --------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.nokeeper4, PID: 3981
    java.lang.RuntimeException: Unable to start activity            ComponentInfo{com.example.nokeeper4/com.example.nokeeper4.MainActivity}: android.view.InflateException:     Binary XML file line #28 in com.example.nokeeper4:layout/activity_main: Binary XML file line #28 in com.example.nokeeper4:layout/activity_main: Error inflating class     androidx.fragment.app.FragmentContainerView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3431)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: android.view.InflateException: Binary XML file line #28 in com.example.nokeeper4:layout/activity_main: Binary XML file line #28 in com.example.nokeeper4:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: android.view.InflateException: Binary XML file line #28 in com.example.nokeeper4:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
     Caused by: java.lang.RuntimeException: Exception inflating com.example.nokeeper4:navigation/nav_graph2 line 15
        at androidx.navigation.NavInflater.inflate(NavInflater.kt:70)
        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:1899)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1823)
        at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1729)
        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)
        at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:227)
        at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1067)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:995)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1121)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:680)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
        at com.example.nokeeper4.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:60)
        at com.example.nokeeper4.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:54)
        at com.example.nokeeper4.MainActivity.onCreate(MainActivity.kt:25)
        at android.app.Activity.performCreate(Activity.java:8000)
E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.UnsupportedOperationException: Cannot add action 0 to Destination(com.example.nokeeper4:id/NoteListActivity) label=Nokeeper4 class=com.example.nokeeper4.NoteListActivity as it does not support actions, indicating that it is a terminal destination in your navigation graph and will never trigger actions.
        at androidx.navigation.NavDestination.putAction(NavDestination.kt:445)
        at androidx.navigation.NavInflater.inflateAction(NavInflater.kt:322)
        at androidx.navigation.NavInflater.inflate(NavInflater.kt:107)
        at androidx.navigation.NavInflater.inflate(NavInflater.kt:114)
        at androidx.navigation.NavInflater.inflate(NavInflater.kt:64)
            ... 39 more
I/Process: Sending signal. PID: 3981 SIG: 9

这是我的项目 nav_graph2.xml 文件。

    <activity
        android:id="@+id/NoteListActivity"
        android:name="com.example.nokeeper4.NoteListActivity"
        android:label="@string/notelist_label"
        tools:layout="@layout/activity_note_list">
    <action
        app:destination="@id/MainActivity"/>
    </activity>
    
    <activity
        android:id="@+id/MainActivity"
        android:name="com.example.nokeeper4.MainActivity"
        android:label="@string/main_label"
        tools:layout="@layout/activity_main">
    
        <action
            app:destination="@id/NoteListActivity" />
    </activity>>

\</navigation\>\`

DataManager.kt 文件。

object DataManager {
val courses = HashMap\<String, CourseInfo\>()
val notes = ArrayList\<NoteInfo\>()

init{
    initializeCourses()
    initializeNotes()
}

private fun initializeCourses(){
    var course = CourseInfo("android_intents","Android Programming with Intents")
    courses.set(course.courseId, course)
    course = CourseInfo("android_async", "Android Async Programming and Services")
    courses.set(course.courseId, course)
    course = CourseInfo("java_lang", "Java Fundamentals: The Java Language")
    courses.set(course.courseId, course)
    course = CourseInfo("java_core", "Java Fundamentals: The core platform")
    courses.set(course.courseId, course)
}
private fun initializeNotes(){

}

}`

activity_note_list.xml 文件。

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".NoteListActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="100dp">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize" />

    </com.google.android.material.appbar.AppBarLayout>


    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"
        android:contentDescription="@string/new_note"
        android:src="@drawable/baseline_add_white_24"
        app:backgroundTint="#9C27B0" />


    <include
        android:id="@+id/contentNoteList"
        layout="@layout/content_note_list" />


</androidx.coordinatorlayout.widget.CoordinatorLayout>

NoteListActivity.kt 文件。

package com.example.nokeeper4

import android.content.Intent
import android.os.Bundle
import android.widget.ArrayAdapter
import android.widget.ListView
import androidx.appcompat.app.AppCompatActivity
import com.example.nokeeper4.databinding.ActivityNoteListBinding

class NoteListActivity : AppCompatActivity() {

    private lateinit var binding: ActivityNoteListBinding
    private lateinit var listNotes: ListView
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)


        binding = ActivityNoteListBinding.inflate(layoutInflater)
        setContentView(binding.root)

        listNotes = findViewById(R.id.listNotes)

        binding.fab.setOnClickListener {
            val activityIntent = Intent(this, MainActivity::class.java)
            startActivity(activityIntent)
        }
        listNotes.adapter = ArrayAdapter(
            this,
            android.R.layout.simple_list_item_1,
            DataManager.notes)

        listNotes.setOnItemClickListener { _, _, position, _ ->
            val activityIntent = Intent(this, MainActivity::class.java)
            activityIntent.putExtra(NOTE_POSITION, position)
            startActivity(activityIntent)

        }
    }

    override fun onResume() {
        super.onResume()
        (listNotes.adapter as ArrayAdapter<*>).notifyDataSetChanged()
    }
}

activity_main.xml 文件。

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/Theme.Nokeeper4.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/Theme.Nokeeper4.PopupOverlay" />

    </com.google.android.material.appbar.AppBarLayout>
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_frag"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:navGraph="@navigation/nav_graph2"/>



    <include
        android:id="@+id/contentMain"
        layout="@layout/content_main" />


</androidx.coordinatorlayout.widget.CoordinatorLayout>

MainActivity.kt 文件。

package com.example.nokeeper4
import android.annotation.SuppressLint
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import android.view.Menu
import android.view.MenuItem
import android.widget.ArrayAdapter
import android.widget.EditText
import android.widget.Spinner
import com.example.nokeeper4.databinding.ActivityMainBinding


class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private var notePosition = POSITION_NOT_SET
    private lateinit var spinnerCourses:  Spinner
    private lateinit var textNoteTitle: EditText
    private lateinit var textNoteText: EditText



    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        setSupportActionBar(binding.toolbar)
        spinnerCourses = findViewById(R.id.spinnerCourses)
        textNoteTitle = findViewById(R.id.textNoteTitle)
        textNoteText = findViewById(R.id.textNoteText)




        val adapterCourses = ArrayAdapter<CourseInfo>(this,
                android.R.layout.simple_spinner_item,
                DataManager.courses.values.toList())
        adapterCourses.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
        spinnerCourses.adapter = adapterCourses

        notePosition = savedInstanceState?.getInt(NOTE_POSITION, POSITION_NOT_SET) ?:
            intent.getIntExtra(NOTE_POSITION,POSITION_NOT_SET)

        if (notePosition != POSITION_NOT_SET)
            displayNote()
        else{
            DataManager.notes.add(NoteInfo())
            notePosition = DataManager.notes.lastIndex
        }
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putInt(NOTE_POSITION, notePosition)
    }

    private fun displayNote() {
        val note = DataManager.notes[notePosition]
        textNoteTitle.setText(note.title)
        textNoteText.setText(note.text)

        val coursePosition = DataManager.courses.values.indexOf(note.course)
        spinnerCourses.setSelection(coursePosition)
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
            R.id.action_settings -> true
            R.id.action_next ->{
                moveNext()
                true
            }
            else -> super.onOptionsItemSelected(item)
        }
    }

    private fun moveNext() {
        ++notePosition
        displayNote()
        invalidateOptionsMenu()
    }

    @SuppressLint("UseCompatLoadingForDrawables")
    override fun onPrepareOptionsMenu(menu: Menu?): Boolean {
        if(notePosition >= DataManager.notes.lastIndex){
            val menuItem = menu?.findItem(R.id.action_next)
            if(menuItem != null){
                menuItem.icon = getDrawable(R.drawable.baseline_block_black_24)
                menuItem.isEnabled = false
            }
        }
        return super.onPrepareOptionsMenu(menu)
        
    }

    override fun onPause() {
        super.onPause()
        saveNote()
    }

    private fun saveNote() {
        val note = DataManager.notes[notePosition]
        note.title = textNoteTitle.text.toString()
        note.text = textNoteText.text.toString()
        note.course = spinnerCourses.selectedItem as CourseInfo
    }
}