Android Studio，覆盖 fun onOptionsItemSelected(...) not navigating to second fragment... 错误没有设置 NavController答案

【问题标题】：Android Studio, override fun onOptionsItemSelected(...) not navigating to second fragment... error of does not have NavController setAndroid Studio，覆盖 fun onOptionsItemSelected(...) not navigating to second fragment... 错误没有设置 NavController
【发布时间】：2022-01-16 00:56:07
【问题描述】：

我的应用有两个片段和主要活动。我正在使用菜单栏图标从主要活动/第一个片段转到第二个片段。

问题是单击图标时发生致命异常，我收到以下错误：

java.lang.IllegalStateException: View androidx.constraintlayout.widget.ConstraintLayout{ccc58e7 V.E...... ........ 0,0-1080,1584} does not have a NavController set

错误在override fun onOptionsItemSelected(item: MenuItem): Boolean 函数中调用了一行。具体线路是：

view?.let { Navigation.findNavController(it).navigate(MainFragmentDirections.actionMainFragmentToNotesFragment3()) }

此代码取自另一个正在运行的应用程序，因此我不明白为什么会出现此错误。

我将不胜感激。

所有代码如下：

MainFragment.kt

package com.genauapps.cis2818_proj4_runningapp

import android.os.Bundle
import android.view.*
import androidx.fragment.app.Fragment
import androidx.navigation.Navigation
import android.view.Menu
import android.view.MenuItem
import android.app.Activity
import android.util.Log

class MainFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        setHasOptionsMenu(true)

        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_main, container, false)
    }

    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
        super.onCreateOptionsMenu(menu, inflater)
        inflater.inflate(R.menu.menu, menu)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item.itemId) {
            R.id.menu_add_workout -> {
                Log.i("test", "Button Clicked")
                view?.let { Navigation.findNavController(it).navigate(MainFragmentDirections.actionMainFragmentToNotesFragment3()) }
            }
        }
        return true
    }
}

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    android:padding="10dp"
    tools:context=".MainFragment"
    android:name="androidx.navigation.fragment.MainFragment"
    >

    <TextView
        android:id="@+id/main_activity_tv_main_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:fontFamily="monospace"
        android:text="@string/text_view_main_title"
        android:textColor="@color/old_mauve"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <View
        android:id="@+id/divider"
        android:layout_width="409dp"
        android:layout_height="1dp"
        android:layout_marginTop="8dp"
        android:background="?android:attr/listDivider"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/main_activity_tv_main_title" />

    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/divider" />
</androidx.constraintlayout.widget.ConstraintLayout>

fragment_notes.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    android:padding="10dp"
    tools:context=".NotesFragment"
    android:name="androidx.navigation.fragment.MainFragment"
    >

    <TextView
        android:id="@+id/notes_fragment_tv_myworkout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="monospace"
        android:text="@string/text_view_myworkout"
        android:textSize="20sp"
        android:textStyle="bold|italic"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/notes_fragment_et_time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:fontFamily="monospace"
        android:hint="@string/edit_text_time"
        android:importantForAutofill="no"
        android:textAlignment="center"
        android:textColor="@color/black"
        android:textColorHint="@color/black"
        android:textSize="34sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_tv_myworkout"
        tools:ignore="TextContrastCheck" />

    <EditText
        android:id="@+id/notes_fragment_et_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:fontFamily="monospace"
        android:hint="@string/edit_text_date"
        android:importantForAutofill="no"
        android:inputType="date"
        android:minHeight="48dp"
        android:textColorHint="@color/black"
        android:textSize="20sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_et_time" />

    <EditText
        android:id="@+id/notes_fragment_et_distance"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:fontFamily="monospace"
        android:hint="@string/edit_text_distance"
        android:inputType="numberDecimal"
        android:textColorHint="@color/black"
        android:textSize="20sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_et_date"
        android:importantForAutofill="no" />

    <EditText
        android:id="@+id/notes_fragment_et_notes"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:fontFamily="monospace"
        android:hint="@string/edit_text_notes"
        android:importantForAutofill="no"
        android:inputType="textCapSentences|textAutoCorrect"
        android:minHeight="48dp"
        android:textColor="@color/black"
        android:textColorHint="@color/black"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_et_distance" />

    <Button
        android:id="@+id/notes_fragment_bt_start_stop"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:backgroundTint="@color/y_in_mn_blue"
        android:fontFamily="monospace"
        android:text="@string/button_text"
        android:textAlignment="center"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_et_notes" />

    <Button
        android:id="@+id/notes_fragment_bt_save"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:backgroundTint="@color/y_in_mn_blue"
        android:fontFamily="monospace"
        android:text="@string/button_text_save"
        android:textAlignment="center"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notes_fragment_bt_start_stop" />

</androidx.constraintlayout.widget.ConstraintLayout>

导航.xml

<?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/mainFragment">
    <fragment
        android:id="@+id/mainFragment"
        android:name="com.genauapps.cis2818_proj4_runningapp.MainFragment"
        android:label="fragment_main"
        tools:layout="@layout/fragment_main" >
        <action
            android:id="@+id/action_mainFragment_to_notesFragment3"
            app:destination="@id/notesFragment3" />
    </fragment>
    <fragment
        android:id="@+id/notesFragment3"
        android:name="com.genauapps.cis2818_proj4_runningapp.NotesFragment"
        android:label="fragment_notes"
        tools:layout="@layout/fragment_notes" >
        <action
            android:id="@+id/action_notesFragment3_to_mainFragment"
            app:destination="@id/mainFragment" />
    </fragment>
</navigation>

menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/menu_add_workout"
        android:icon="@drawable/ic_baseline_run_circle_24"
        android:title="@string/menu_add_workout"
        app:showAsAction="ifRoom" />
</menu>

Logcat

2021-12-11 17:24:18.121 27715-27715/com.genauapps.cis2818_proj4_runningapp I/test: Button Clicked
2021-12-11 17:24:18.125 27715-27715/com.genauapps.cis2818_proj4_runningapp D/AndroidRuntime: Shutting down VM
2021-12-11 17:24:18.126 27715-27715/com.genauapps.cis2818_proj4_runningapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.genauapps.cis2818_proj4_runningapp, PID: 27715
    java.lang.IllegalStateException: View androidx.constraintlayout.widget.ConstraintLayout{ccc58e7 V.E...... ........ 0,0-1080,1584} does not have a NavController set
        at androidx.navigation.Navigation.findNavController(Navigation.java:84)
        at androidx.navigation.fragment.NavHostFragment.findNavController(NavHostFragment.java:120)
        at androidx.navigation.fragment.FragmentKt.findNavController(Fragment.kt:29)
        at com.genauapps.cis2818_proj4_runningapp.MainFragment.onOptionsItemSelected(MainFragment.kt:56)
        at androidx.fragment.app.Fragment.performOptionsItemSelected(Fragment.java:3154)
        at androidx.fragment.app.FragmentManager.dispatchOptionsItemSelected(FragmentManager.java:2937)
        at androidx.fragment.app.FragmentController.dispatchOptionsItemSelected(FragmentController.java:427)
        at androidx.fragment.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:334)
        at androidx.appcompat.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:264)
        at androidx.appcompat.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:109)
        at androidx.appcompat.app.AppCompatDelegateImpl.onMenuItemSelected(AppCompatDelegateImpl.java:1185)
        at androidx.appcompat.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:834)
        at androidx.appcompat.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:158)
        at androidx.appcompat.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:985)
        at androidx.appcompat.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:975)
        at androidx.appcompat.widget.ActionMenuView.invokeItem(ActionMenuView.java:625)
        at androidx.appcompat.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:151)
        at android.view.View.performClick(View.java:7448)
        at android.view.View.performClickInternal(View.java:7425)
        at android.view.View.access$3600(View.java:810)
        at android.view.View$PerformClick.run(View.java:28305)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        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)

【问题讨论】：

从您的错误消息来看，您似乎使用FragmentTransaction 直接将您的MainFragment 添加到您的活动中，而不是通过NavHostFragment。能否包含活动的onCreate() 和活动的布局 XML？

标签： android android-fragments android-navigation

【解决方案1】：

根据@ianhanniballake 的评论：

在activity_main.xml 中，我将FragmentContainerView 更改为NavHostFragment 容器，它解决了这个问题。

【讨论】：