当我开始使用导航组件时，应用程序崩溃了。它无法正确地膨胀fragmentContaner视图。 主要活动 kotlin
package com.example.task2
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.navigation.NavController
import androidx.navigation.NavHost
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.setupWithNavController
import com.example.task2.databinding.ActivityMainBinding
class MainActivity : AppCompatActivity() {
lateinit var binding: ActivityMainBinding
lateinit var navController: NavController
override fun onCreate(savedInstanceState: Bundle?) {
binding = ActivityMainBinding.inflate(layoutInflater)
super.onCreate(savedInstanceState)
setContentView(binding.root)
binding.bottomNavMain.menu.findItem(R.id.fragmentHome).isChecked = true
//nav component
val navHost = supportFragmentManager.findFragmentById(R.id.main_nav_host) as NavHostFragment
navController=navHost.navController
binding.bottomNavMain.setupWithNavController(navController)
}
}
主要活动 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"
tools:context=".MainActivity">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottom_nav_main"
android:layout_width="match_parent"
android:layout_height="56dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_nav"
style="@style/Widget.MaterialComponents.BottomNavigationView.Colored"
app:backgroundTint="?attr/colorPrimaryVariant"/>
<androidx.fragment.app.FragmentContainerView
android:id="@+id/main_nav_host"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toTopOf="@id/bottom_nav_main"
android:layout_marginBottom="56dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:defaultNavHost="true"
app:navGraph="@navigation/main_nav"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>
导航图：
<?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/main_nav"
app:startDestination="@id/fragmentHome">
<fragment
android:id="@+id/fragmentHome"
android:name="com.example.task2.fragment.FragmentHome"
android:label="FragmentHome"
tools:layout="@layout/home_fragment"/>
<fragment
android:id="@+id/fragmentRegister"
android:name="com.example.task2.fragment.FragmentRegister"
android:label="FragmentRegister"
tools:layout="@layout/register_fragment">
<action
android:id="@+id/action_fragmentRegister_to_fragmentLogin"
app:destination="@id/fragmentLogin" />
</fragment>
<fragment
android:id="@+id/fragmentProfile"
android:name="com.example.task2.fragment.FragmentProfile"
android:label="FragmentProfile"
tools:layout="@layout/profile_fragment"/>
<fragment
android:id="@+id/fragmentLogin"
android:name="com.example.task2.fragment.FragmentLogin"
android:label="FragmentLogin"
tools:layout="@layout/login_fragment">
<action
android:id="@+id/action_fragmentLogin_to_fragmentRegister"
app:destination="@id/fragmentRegister" />
</fragment>
</navigation>
底部导航：
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/fragmentRegister"
android:title="Register"
android:icon="@drawable/register" />
<item
android:title="Home"
android:id="@+id/fragmentHome"
android:icon="@drawable/home" />
<item
android:title="Profile"
android:id="@+id/fragmentProfile"
android:icon="@drawable/profile" />
</menu>
并显示错误：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.task2/com.example.task2.MainActivity}: android.view.InflateException: Binary XML file line #32 in com.example.task2:layout/activity_main: Binary XML file line #32 in com.example.task2:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
这是错误的确切消息：
FATAL EXCEPTION: main
Process: com.example.task2, PID: 14548
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.task2/com.example.task2.MainActivity}: android.view.InflateException: Binary XML file line #32 in com.example.task2:layout/activity_main: Binary XML file line #32 in com.example.task2:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4169)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4325)
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$H.handleMessage(ActivityThread.java:2574)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:226)
at android.os.Looper.loop(Looper.java:313)
at android.app.ActivityThread.main(ActivityThread.java:8757)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1067)
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.task2:layout/activity_main: Binary XML file line #32 in com.example.task2:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.task2:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context androidx.fragment.app.FragmentHostCallback.getContext()' on a null object reference
at androidx.fragment.app.FragmentManager$3.instantiate(FragmentManager.java:525)
at androidx.fragment.app.FragmentContainerView.<init>(FragmentContainerView.kt:153)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:53)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:136)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:247)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:226)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1091)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1019)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:983)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1145)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1106)
at android.view.LayoutInflater.inflate(LayoutInflater.java:692)
at android.view.LayoutInflater.inflate(LayoutInflater.java:544)
at com.example.task2.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:50)
at com.example.task2.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:44)
at com.example.task2.MainActivity.onCreate(MainActivity.kt:15)
at android.app.Activity.performCreate(Activity.java:8591)
at android.app.Activity.performCreate(Activity.java:8570)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1384)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4150)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4325)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2574)
at android.os.Handler.dispatchMessage(Handler.java:106)
--------- beginning of system
2023-11-05 11:03:21.125 1440-1971 WindowManager system_server E win=Window{18fadc7 u0 com.example.task2/com.example.task2.SplashScreen} destroySurfaces: appStopped=true cleanupOnResume=false win.mWindowRemovalAllowed=false win.mRemoveOnExit=false win.mViewVisibility=4 caller=com.android.server.wm.ActivityRecord.destroySurfaces:6529 com.android.server.wm.ActivityRecord.destroySurfaces:6510 com.android.server.wm.ActivityRecord.notifyAppStopped:6574 com.android.server.wm.ActivityRecord.activityStopped:7162 com.android.server.wm.ActivityClientController.activityStopped:258 android.app.IActivityClientController$Stub.onTransact:613 com.android.server.wm.ActivityClientController.onTransact:136
2023-11-05 11:03:21.147 1440-1971 WindowManager system_server E win=Window{40ab30d u0 Splash Screen com.example.task2} destroySurfaces: appStopped=true cleanupOnResume=false win.mWindowRemovalAllowed=false win.mRemoveOnExit=false win.mViewVisibility=8 caller=com.android.server.wm.WindowManagerService.tryStartExitingAnimation:3009 com.android.server.wm.WindowManagerService.relayoutWindow:2720 com.android.server.wm.Session.relayout:274 android.view.IWindowSession$Stub.onTransact:779 com.android.server.wm.Session.onTransact:188 android.os.Binder.execTransactInternal:1321 android.os.Binder.execTransact:1280
我尝试使用
我复制了你的项目，经过 30 分钟的拉扯我的头发，我终于看到了它。
您需要先致电
super.onCreate(savedInstanceState) super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.bottomNavMain.menu.findItem(R.id.fragmentHome).isChecked = true