实现底部导航栏与ViewPager的联动效果，主要包含以下三个核心模块：

1. 主界面布局设计
2. Fragment适配器开发
3. 按钮状态同步机制

public class MyFragmentPagerAdapter extends FragmentStateAdapter {
    private List<Fragment> fragmentsList = new ArrayList<>();

    public MyFragmentPagerAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle, List<Fragment> fragments) {
        super(fragmentManager, lifecycle);
        this.fragmentsList = fragments;
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        return fragmentsList.get(position);
    }

    @Override
    public int getItemCount() {
        return fragmentsList.size();
    }
}

private void initPager() {
    ViewPager2 viewPager = findViewById(R.id.viewpager);
    ArrayList<Fragment> fragmentList = new ArrayList<>();
    
    fragmentList.add(BlankFragment.create("微信聊天"));
    fragmentList.add(BlankFragment.create("通讯录"));
    fragmentList.add(BlankFragment.create("朋友圈"));
    fragmentList.add(BlankFragment.create("个人中心"));
    
    MyFragmentPagerAdapter adapter = new MyFragmentPagerAdapter(
        getSupportFragmentManager(), 
        getLifecycle(), 
        fragmentList
    );
    viewPager.setAdapter(adapter);
    
    viewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
        @Override
        public void onPageSelected(int position) {
            updateTabIndicator(position);
        }
    });
}

private void initTabs() {
    View tabChat = findViewById(R.id.tab_chat);
    View tabContact = findViewById(R.id.tab_contact);
    View tabFind = findViewById(R.id.tab_find);
    View tabProfile = findViewById(R.id.tab_profile);
    
    tabChat.setSelected(true);
    currentTab = tabChat;
    
    tabChat.setOnClickListener(v -> {
        viewPager.setCurrentItem(0, false);
        updateTabState(tabChat);
    });
    
    // 其他按钮的初始化和点击事件类似
}

private void updateTabIndicator(int position) {
    if (currentTab != null) {
        currentTab.setSelected(false);
    }
    
    switch (position) {
        case 0:
            updateTabState(findViewById(R.id.tab_chat));
            break;
        case 1:
            updateTabState(findViewById(R.id.tab_contact));
            break;
        case 2:
            updateTabState(findViewById(R.id.tab_find));
            break;
        case 3:
            updateTabState(findViewById(R.id.tab_profile));
            break;
    }
}

private void updateTabState(View tab) {
    tab.setSelected(true);
    currentTab = tab;
}

public class BlankFragment extends Fragment {
    private static final String ARG_TITLE = "title";
    private View rootView;
    private String pageTitle;

    public static BlankFragment create(String title) {
        BlankFragment fragment = new BlankFragment();
        Bundle args = new Bundle();
        args.putString(ARG_TITLE, title);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
                             Bundle savedInstanceState) {
        if (rootView == null) {
            rootView = inflater.inflate(R.layout.fragment_blank, container, false);
        }
        initView();
        return rootView;
    }

    private void initView() {
        TextView titleView = rootView.findViewById(R.id.title_text);
        pageTitle = getArguments().getString(ARG_TITLE);
        titleView.setText(pageTitle);
    }
}