android 当我在 activity 中使用 navHostFragment 时，应用程序将停止
android application will stop when I use navHostFragment in my activity
我想通过在主 activity 中使用 navHostFragment 来使用导航底部菜单。但是当我 运行 程序时，它在 onCreat 方法 MainActivity java 代码中的 setContent 上停止。
我尝试直接使用 bindig class insted setContent 但没有任何变化。
这是MainActivity.java
package com.example.omarket.ui.fragments;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import com.example.omarket.R;
public class MainActivity extends AppCompatActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // <--- it stops here, i use debuger to understand it.
}
}
这是activity_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:paddingTop="?attr/actionBarSize"
android:id="@+id/container">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/nav_host_bottom"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="@drawable/navigation_bar_background"
app:itemIconSize="@dimen/large_icon_size"
app:itemIconTint="@color/black"
app:labelVisibilityMode="unlabeled"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_navigation_menu" />
<fragment
android:id="@+id/nav_host_fragment_activity_main"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@id/nav_host_bottom"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/navigation_main_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
navigation_main_graph.xml 在导航目录中：
<?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_main_graph"
app:startDestination="@id/homeFragment">
<fragment
android:id="@+id/settingFragment"
android:name="com.example.omarket.ui.fragments.settings.SettingFragment"
android:label="@string/title_settings"
tools:layout="@layout/fragment_setting" />
<fragment
android:id="@+id/favoriteFragment"
android:name="com.example.omarket.ui.fragments.favorites.FavoriteFragment"
android:label="@string/title_favorite"
tools:layout="@layout/fragment_favorite" />
<fragment
android:id="@+id/productsFragment"
android:name="com.example.omarket.ui.fragments.products.ProductsFragment"
android:label="@string/title_products"
tools:layout="@layout/fragment_products" />
<fragment
android:id="@+id/homeFragment"
android:name="com.example.omarket.ui.fragments.home.HomeFragment"
android:label="@string/title_home"
tools:layout="@layout/fragment_home"/>
<fragment
android:id="@+id/dashboardFragment"
android:name="com.example.omarket.ui.fragments.dashboard.DashboardFragment"
android:label="fragment_dashboard"
tools:layout="@layout/fragment_dashboard" />
</navigation>
我遇到的错误
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.omarket, PID: 8090
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.omarket/com.example.omarket.ui.fragments.MainActivity}: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.omarket.ui.fragments.home.HomeFragment: could not find Fragment constructor
at androidx.fragment.app.Fragment.instantiate(Fragment.java:628)
at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57)
at androidx.fragment.app.FragmentManager.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:1066)
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:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:140)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
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)
E/AndroidRuntime: at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:699)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at com.example.omarket.ui.fragments.MainActivity.onCreate(MainActivity.java:26)
at android.app.Activity.performCreate(Activity.java:8000)
at android.app.Activity.performCreate(Activity.java:7984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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: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)
Caused by: java.lang.NoSuchMethodException: com.example.omarket.ui.fragments.home.HomeFragment.<init> []
at java.lang.Class.getConstructor0(Class.java:2332)
at java.lang.Class.getConstructor(Class.java:1728)
at androidx.fragment.app.Fragment.instantiate(Fragment.java:613)
... 46 more
在使用 navHostFragment 之前，当我使用框架布局时它可以工作。
有什么解决办法吗？
您的 HomeFragment 似乎没有无参数构造函数。
如果您想使用需要构造函数参数的片段，您需要向导航组件提供 FragmentFactory。
将空构造函数 HomeFragment() 添加到 HomeFragment，它应该可以工作。
我想通过在主 activity 中使用 navHostFragment 来使用导航底部菜单。但是当我 运行 程序时，它在 onCreat 方法 MainActivity java 代码中的 setContent 上停止。 我尝试直接使用 bindig class insted setContent 但没有任何变化。
这是MainActivity.java
package com.example.omarket.ui.fragments;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import com.example.omarket.R;
public class MainActivity extends AppCompatActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // <--- it stops here, i use debuger to understand it.
}
}
这是activity_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:paddingTop="?attr/actionBarSize"
android:id="@+id/container">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/nav_host_bottom"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="@drawable/navigation_bar_background"
app:itemIconSize="@dimen/large_icon_size"
app:itemIconTint="@color/black"
app:labelVisibilityMode="unlabeled"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="@menu/bottom_navigation_menu" />
<fragment
android:id="@+id/nav_host_fragment_activity_main"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@id/nav_host_bottom"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/navigation_main_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
navigation_main_graph.xml 在导航目录中：
<?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_main_graph"
app:startDestination="@id/homeFragment">
<fragment
android:id="@+id/settingFragment"
android:name="com.example.omarket.ui.fragments.settings.SettingFragment"
android:label="@string/title_settings"
tools:layout="@layout/fragment_setting" />
<fragment
android:id="@+id/favoriteFragment"
android:name="com.example.omarket.ui.fragments.favorites.FavoriteFragment"
android:label="@string/title_favorite"
tools:layout="@layout/fragment_favorite" />
<fragment
android:id="@+id/productsFragment"
android:name="com.example.omarket.ui.fragments.products.ProductsFragment"
android:label="@string/title_products"
tools:layout="@layout/fragment_products" />
<fragment
android:id="@+id/homeFragment"
android:name="com.example.omarket.ui.fragments.home.HomeFragment"
android:label="@string/title_home"
tools:layout="@layout/fragment_home"/>
<fragment
android:id="@+id/dashboardFragment"
android:name="com.example.omarket.ui.fragments.dashboard.DashboardFragment"
android:label="fragment_dashboard"
tools:layout="@layout/fragment_dashboard" />
</navigation>
我遇到的错误
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.omarket, PID: 8090
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.omarket/com.example.omarket.ui.fragments.MainActivity}: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #33 in com.example.omarket:layout/activity_main: Error inflating class fragment
Caused by: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.omarket.ui.fragments.home.HomeFragment: could not find Fragment constructor
at androidx.fragment.app.Fragment.instantiate(Fragment.java:628)
at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57)
at androidx.fragment.app.FragmentManager.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:1066)
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:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:140)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
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)
E/AndroidRuntime: at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:699)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at com.example.omarket.ui.fragments.MainActivity.onCreate(MainActivity.java:26)
at android.app.Activity.performCreate(Activity.java:8000)
at android.app.Activity.performCreate(Activity.java:7984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.NoSuchMethodException: com.example.omarket.ui.fragments.home.HomeFragment.<init> []
at java.lang.Class.getConstructor0(Class.java:2332)
at java.lang.Class.getConstructor(Class.java:1728)
at androidx.fragment.app.Fragment.instantiate(Fragment.java:613)
... 46 more
在使用 navHostFragment 之前，当我使用框架布局时它可以工作。 有什么解决办法吗？
您的 HomeFragment 似乎没有无参数构造函数。
如果您想使用需要构造函数参数的片段，您需要向导航组件提供 FragmentFactory。
将空构造函数 HomeFragment() 添加到 HomeFragment，它应该可以工作。