实现菜单项从main到fragment

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

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int itemId = item.getItemId();
    Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);

    switch (itemId) {
        case R.id.menu_item1:
            if (currentFragment instanceof Fragment1) {
                // 当前显示的是Fragment1，执行相应操作
                ((Fragment1) currentFragment).doSomething();
            } else {
                // 导航到Fragment1
                getSupportFragmentManager().beginTransaction()
                        .replace(R.id.fragment_container, new Fragment1())
                        .commit();
            }
            return true;
        case R.id.menu_item2:
            if (currentFragment instanceof Fragment2) {
                // 当前显示的是Fragment2，执行相应操作
                ((Fragment2) currentFragment).doSomething();
            } else {
                // 导航到Fragment2
                getSupportFragmentManager().beginTransaction()
                        .replace(R.id.fragment_container, new Fragment2())
                        .commit();
            }
            return true;
        // 其他菜单项的处理...
        default:
            return super.onOptionsItemSelected(item);
    }
}

public class Fragment1 extends Fragment {
    // ...

    public void doSomething() {
        // 执行相应操作
    }
}

public class Fragment2 extends Fragment {
    // ...

    public void doSomething() {
        // 执行相应操作
    }
}