用fragment组件制作一个底部导航栏

好的，可以使用BottomNavigationView组件来实现底部导航栏。首先在布局文件中添加BottomNavigationView组件，然后使用FragmentTransaction将对应的Fragment添加到页面中。以下是一个简单的实现示例：

1. 在布局文件中添加BottomNavigationView组件

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/navigation_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    app:menu="@menu/navigation_menu" />

2. 在Activity中设置BottomNavigationView的选项卡并添加对应的Fragment

public class MainActivity extends AppCompatActivity {
    private FragmentManager fragmentManager = getSupportFragmentManager();
    private Fragment fragmentHome = new HomeFragment();
    private Fragment fragmentNews = new NewsFragment();
    private Fragment fragmentSettings = new SettingsFragment();
    private BottomNavigationView navigationView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 初始化BottomNavigationView
        navigationView = findViewById(R.id.navigation_view);
        navigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                switch (menuItem.getItemId()) {
                    case R.id.menu_home:
                        replaceFragment(fragmentHome);
                        return true;
                    case R.id.menu_news:
                        replaceFragment(fragmentNews);
                        return true;
                    case R.id.menu_settings:
                        replaceFragment(fragmentSettings);
                        return true;
                }
                return false;
            }
        });

        // 首次加载显示默认Fragment
        fragmentManager.beginTransaction().replace(R.id.fragment_container, fragmentHome).commit();
    }

    private void replaceFragment(Fragment fragment) {
        fragmentManager.beginTransaction().replace(R.id.fragment_container, fragment).commit();
    }
}

3. 创建对应的Fragment

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

public class NewsFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_news, container, false);
        return view;
    }
}

public class SettingsFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_settings, container, false);
        return view;
    }
}

4. 最后在menu文件夹下创建navigation_menu.xml文件

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/menu_home"
        android:icon="@drawable/ic_home"
        android:title="Home" />
    <item
        android:id="@+id/menu_news"
        android:icon="@drawable/ic_news"
        android:title="News" />
    <item
        android:id="@+id/menu_settings"
        android:icon="@drawable/ic_settings"
        android:title="Settings" />
</menu>

这样，就可以在底部导航栏中添加无数选项卡，并且在点击对应选项卡时自动切换对应的Fragment了。