如何在bottomnavigationview页面写入内容

可以通过以下步骤在BottomNavigationView页面中写入内容：

1. 在布局文件中添加BottomNavigationView控件，例如：

   <com.google.android.material.bottomnavigation.BottomNavigationView
       android:id="@+id/bottom_navigation"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_gravity="bottom"
       app:menu="@menu/bottom_navigation_menu" />

2. 创建要在BottomNavigationView中显示的Fragment，例如：

   public class HomeFragment extends Fragment {
       @Override
       public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                Bundle savedInstanceState) {
           return inflater.inflate(R.layout.fragment_home, container, false);
       }
   }

3. 创建菜单资源文件bottom_navigation_menu.xml，定义BottomNavigationView的菜单项和对应的Fragment，例如：

   <menu xmlns:android="http://schemas.android.com/apk/res/android">
       <item
           android:id="@+id/menu_home"
           android:icon="@drawable/ic_home"
           android:title="@string/menu_home" />
       <item
           android:id="@+id/menu_dashboard"
           android:icon="@drawable/ic_dashboard"
           android:title="@string/menu_dashboard" />
       <item
           android:id="@+id/menu_notifications"
           android:icon="@drawable/ic_notifications"
           android:title="@string/menu_notifications" />
   </menu>

4. 在MainActivity中设置BottomNavigationView的菜单和点击事件处理，例如：

   public class MainActivity extends AppCompatActivity {
       private BottomNavigationView bottomNavigationView;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
   
           bottomNavigationView = findViewById(R.id.bottom_navigation);
           bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
               @Override
               public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                   switch (item.getItemId()) {
                       case R.id.menu_home:
                           getSupportFragmentManager().beginTransaction()
                                   .replace(R.id.fragment_container, new HomeFragment())
                                   .commit();
                           return true;
                       case R.id.menu_dashboard:
                           getSupportFragmentManager().beginTransaction()
                                   .replace(R.id.fragment_container, new DashboardFragment())
                                   .commit();
                           return true;
                       case R.id.menu_notifications:
                           getSupportFragmentManager().beginTransaction()
                                   .replace(R.id.fragment_container, new NotificationsFragment())
                                   .commit();
                           return true;
                   }
                   return false;
               }
           });
   
           // 默认显示HomeFragment
           getSupportFragmentManager().beginTransaction()
                   .replace(R.id.fragment_container, new HomeFragment())
                   .commit();
       }
   }

5. 在MainActivity的布局文件中添加一个FrameLayout作为Fragment的容器，例如：

   <FrameLayout
       android:id="@+id/fragment_container"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:layout_above="@id/bottom_navigation" />

通过以上步骤，就可以在BottomNavigationView页面中显示对应的Fragment内容了。