我决定对我的应用程序执行Firebase Robo测试,发现当打开外部活动然后返回到应用程序时,它总是崩溃。通过在开发者选项中启用“不保留活动”来复制问题。
崩溃:
这是一个令人沮丧的问题,我无法解决。我尝试移除 NavigationView.OnNavigationItemSelectedListener 监听器,虽然可以正常工作,但我需要该监听器用于其他控件,例如片段切换动画和抽屉布局转换。
崩溃:
java.lang.ClassCastException: com.example.problemtesting.Fragments.Fragment_2 无法强制转换为 androidx.navigation.fragment.NavHostFragment
这表明问题是由以下代码行引起的:NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
如何复制问题:
- 启用“不保留活动”
- 打开应用程序然后打开应用程序抽屉
- 选择“片段2”
- 按分享按钮
- 按消息按钮(或任何其他外部应用)
- 返回应用程序(崩溃)
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
DrawerLayout drawer;
NavigationView navigationView;
FragmentManager fragmentManager;
AppBarConfiguration mAppBarConfiguration;
NavController navController;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentManager = getSupportFragmentManager();
drawer = findViewById(R.id.drawer_layout);
navigationView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
mAppBarConfiguration = new AppBarConfiguration.Builder(
R.id.nav_fragment_1, R.id.nav_fragment_2)
.setOpenableLayout(drawer)
.build();
NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
if (navHostFragment != null)
navController = navHostFragment.getNavController();
else navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(MainActivity.this, navController, mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView, navController);
setNavigationViewListener();
}
@Override
public boolean onSupportNavigateUp() {
return NavigationUI.navigateUp(navController, mAppBarConfiguration)
|| super.onSupportNavigateUp();
}
private void setNavigationViewListener() {
navigationView.setNavigationItemSelectedListener(MainActivity.this);
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.nav_fragment_1: {
fragmentManager.beginTransaction()
.replace(R.id.nav_host_fragment, new Fragment_1())
.commitNow();
MainActivity.this.setTitle("Fragment 1");
break;
}
case R.id.nav_fragment_2: {
fragmentManager.beginTransaction()
.replace(R.id.nav_host_fragment, new Fragment_2())
.commitNow();
MainActivity.this.setTitle("Fragment 2");
break;
}
}
drawer.closeDrawers();
return true;
}
}
片段1
public class Fragment_1 extends Fragment{
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
container.removeAllViews();
View root = inflater.inflate(R.layout.fragment_1, container, false);
return root;
}
}
碎片 2
public class Fragment_2 extends Fragment {
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
container.removeAllViews();
View root = inflater.inflate(R.layout.fragment_2, container, false);
Button share = root.findViewById(R.id.share);
share.setOnClickListener(view -> {
Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("text/plain");
intent.putExtra(Intent.EXTRA_SUBJECT, "Subject");
intent.putExtra(Intent.EXTRA_TEXT, "Message");
startActivity(Intent.createChooser(intent, "Title"));
});
return root;
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start"
>
<androidx.fragment.app.FragmentContainerView
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:tag="my_fragment"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:defaultNavHost="true"
app:navGraph="@navigation/mobile_navigation"
/>
<com.google.android.material.navigation.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_main"
app:menu="@menu/main_drawer"
/>
</androidx.drawerlayout.widget.DrawerLayout>
mobile_navigation.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"
app:startDestination="@+id/nav_fragment_1">
<fragment
android:id="@+id/nav_fragment_1"
android:name="com.example.problemtesting.Fragments.Fragment_1"
tools:layout="@layout/fragment_1"
/>
<fragment
android:id="@+id/nav_fragment_2"
android:name="com.example.problemtesting.Fragments.Fragment_2"
tools:layout="@layout/fragment_2"
/>
</navigation>
main_drawer.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:showIn="navigation_view">
<group android:checkableBehavior="single">
<item
android:id="@+id/nav_fragment_1"
android:title="Fragment 1" />
<item
android:id="@+id/nav_fragment_2"
android:title="Fragment 2" />
</group>
</menu>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.problemtesting">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name="com.example.problemtesting.MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是一个令人沮丧的问题,我无法解决。我尝试移除 NavigationView.OnNavigationItemSelectedListener 监听器,虽然可以正常工作,但我需要该监听器用于其他控件,例如片段切换动画和抽屉布局转换。
onNavigationItemSelected()
调用NavigationUI.onNavDestinationSelected()
,所以调用它以保持行为一致。 - ianhanniballake