写一个包含fragment的安卓程序实现QQ的底部点击切换功能

以下是一个简单的实现底部点击切换功能的安卓程序，使用了Fragment。在这个示例中，我们实现了QQ的底部导航栏的功能。

1. 在activity_main.xml文件中添加BottomNavigationView和FrameLayout：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/navigation" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@color/colorPrimary"
        app:itemIconTint="@color/white"
        app:itemTextColor="@color/white"
        app:menu="@menu/navigation" />

</RelativeLayout>

2. 在menu文件夹中创建navigation.xml文件，添加菜单项：

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_home_black_24dp"
        android:title="@string/title_home" />
    <item
        android:id="@+id/navigation_dashboard"
        android:icon="@drawable/ic_dashboard_black_24dp"
        android:title="@string/title_dashboard" />
    <item
        android:id="@+id/navigation_notifications"
        android:icon="@drawable/ic_notifications_black_24dp"
        android:title="@string/title_notifications" />
</menu>

3. 创建三个Fragment，分别对应底部导航栏的三个选项，例如HomeFragment、DashboardFragment和NotificationsFragment。

4. 在MainActivity中实现底部导航栏的点击事件，并切换到相应的Fragment：

public class MainActivity extends AppCompatActivity {
    private BottomNavigationView bottomNavigationView;
    private FragmentManager fragmentManager;
    private HomeFragment homeFragment;
    private DashboardFragment dashboardFragment;
    private NotificationsFragment notificationsFragment;

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

        bottomNavigationView = findViewById(R.id.navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                switch (menuItem.getItemId()) {
                    case R.id.navigation_home:
                        fragmentManager.beginTransaction().replace(R.id.frame_container, homeFragment).commit();
                        return true;
                    case R.id.navigation_dashboard:
                        fragmentManager.beginTransaction().replace(R.id.frame_container, dashboardFragment).commit();
                        return true;
                    case R.id.navigation_notifications:
                        fragmentManager.beginTransaction().replace(R.id.frame_container, notificationsFragment).commit();
                        return true;
                }
                return false;
            }
        });

        fragmentManager = getSupportFragmentManager();
        homeFragment = new HomeFragment();
        dashboardFragment = new DashboardFragment();
        notificationsFragment = new NotificationsFragment();

        fragmentManager.beginTransaction().replace(R.id.frame_container, homeFragment).commit();
    }
}

这样，当用户点击底部导航栏的选项时，就会切换到相应的Fragment。