在Android中进行数据绑定时，替换片段时工具栏消失

Question

为了保持相同的导航菜单，我将用片段替换主活动的布局。然而，我已经将数据绑定到fragment_home.xml，现在工具栏不再显示，尽管我仍然切换到预期的片段。经过一些调试，我相信这与HomeFragment.java中的setContentView有关。

有什么想法吗？

这是我的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"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity"
tools:openDrawer="start">
<LinearLayout
android:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#000"
android:elevation="4dp"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
<FrameLayout
android:id="@+id/frag_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<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"
app:headerLayout="@layout/nav_header"
app:menu="@menu/side_navbar"
app:itemTextColor="@color/black"
app:itemIconTint="@color/black"/>
</androidx.drawerlayout.widget.DrawerLayout>

用碎片替换帧布局

getSupportFragmentManager().beginTransaction().replace(R.id.frag_container, new HomeFragment()).commit(); ```

和fragment_home.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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"
tools:context=".HomeFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/viewCities"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:padding="4dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</layout>

最后是HomeFragment.java

public class HomeFragment extends Fragment {
private CityViewModel cityViewModel;
private RetrofitAdapter retrofitAdapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
View view = inflater.inflate(R.layout.fragment_home, container, false);
FragmentHomeBinding activityMainBinding =
DataBindingUtil.setContentView(getActivity(), R.layout.fragment_home);
RecyclerView recyclerView = activityMainBinding.viewCities;
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setHasFixedSize(true);
cityViewModel = new ViewModelProvider(requireActivity()).get(CityViewModel.class);
retrofitAdapter = new RetrofitAdapter();
recyclerView.setAdapter(retrofitAdapter);
return view;
}
}

Answer 1

您不必从片段中再次设置内容视图。从HomeFragnent中使用数据绑定，只需执行以下操作即可。

FragmentHomeBinding binding; // declare the binding variable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil
.inflate(inflater, R.layout.fragment_home, container, false);
/* FragmentHomeBinding activityMainBinding =
DataBindingUtil.setContentView(getActivity(), R.layout.fragment_home); */ 
RecyclerView recyclerView = binding.viewCities; // use the binding here
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setHasFixedSize(true);
cityViewModel = new ViewModelProvider(requireActivity()).get(CityViewModel.class);
retrofitAdapter = new RetrofitAdapter();
recyclerView.setAdapter(retrofitAdapter);
return binding.getRoot();
}