TabLayout 的选项卡未显示

我有一个主要活动，它托管一个片段，该片段又托管一个 TabLayout （带有 ViewPager）。显示选项卡栏，但不显示选项卡本身。

这是我在主要活动中用于显示主机片段的代码：

        Fragment fragment = new BMITabsFragment();

        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).addToBackStack(Constants.BMI_TABS_FRAGMENT).commit();

这是我的托管 TabLayout 的片段，即 BMITabsFragment (s.a.)：

public class BMITabsFragment extends Fragment {
...
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }

}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    // Get the ViewPager and set it's PagerAdapter so that it can display items
    ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);
    viewPager.setAdapter(new BMIFragmentPagerAdapter(getActivity().getSupportFragmentManager(),
            getActivity()));

    // Give the TabLayout the ViewPager
    TabLayout tabLayout = (TabLayout) view.findViewById(R.id.sliding_tabs);
    tabLayout.setupWithViewPager(viewPager);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_bmitabs, container, false);
    return view;
}
...
}

这是我的 FragmentPagerAdapter：

public class BMIFragmentPagerAdapter extends FragmentPagerAdapter {

final int PAGE_COUNT = 2;
private FragmentManager fragmentManager;
private Context context;

public BMIFragmentPagerAdapter(FragmentManager fm, Context context) {
    super(fm);
    this.context = context;
    this.fragmentManager = fm;

}

public BMIFragmentPagerAdapter(FragmentManager fm) {
    super(fm);
    fragmentManager = fm;

}

@Override
public CharSequence getPageTitle(int position) {
    String[] pageTitles = context.getResources().getStringArray(R.array.page_titles_array);
    return pageTitles[position];
}

@Override
public Fragment getItem(int position) {
    SharedPreferences prefs = context.getSharedPreferences(Constants.SHARED_PREFS_FILE, 0);
    long patientId = prefs.getLong(Constants.SELECTED_PATIENT_ID, 1);
    Fragment fragment = null;
    switch (position){
        case 0:
            return BMITabelleFragment.newInstance(patientId);

        case 1:
            return BMIChartFragment.newInstance(patientId);

        default:
            return BMITabelleFragment.newInstance(patientId);
    }
}

@Override
public int getCount() {
    return PAGE_COUNT;
}
}

这是fragment_bmitabs.xml：

<?xml version="1.0" encoding="utf-8"?>

<android.support.design.widget.TabLayout
    android:id="@+id/sliding_tabs"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:tabMode="scrollable" />

<android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_height="0px"
    android:layout_weight="1"
    android:background="@android:color/white" />

</LinearLayout>

我的代码基于 Google Android 指南：https://github.com/codepath/android_guides/wiki/Google-Play-Style-Tabs-using-TabLayout

我在这里缺少什么？

注意：我正在使用 AppCompatActivity 以及支持库 v4 和 v7 以及 com:android:support:design 库

这为我解决了这个问题：

tabLayout.post(new Runnable() {
    @Override
    public void run() {
        tabLayout.setupWithViewPager(viewPager);
    }
});

https://code.google.com/p/android/issues/detail?id=180462