title: Android Tablayout no tab titles after pairing with viewpager
body: <p>I am simply trying to pair up with TabLayout with a ViewPager. The pairing is almost working, however the Tabtexts are gone afterwards.</p>
  
  <p>Layout:
      </p>
  
  <pre><code>            &lt;android.support.design.widget.TabItem
                  android:id="@+id/group_tab_orders"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
  
                  android:text="@string/orders"/&gt;
  
              &lt;android.support.design.widget.TabItem
                  android:id="@+id/group_tab_members"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="@string/members"/&gt;
  
              &lt;android.support.design.widget.TabItem
                  android:id="@+id/group_tab_meals"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="@string/meals"/&gt;
  
          &lt;/android.support.design.widget.TabLayout&gt;
  
          &lt;android.support.v4.view.ViewPager
              android:id="@+id/group_viewpager"
              android:layout_width="match_parent"
              android:layout_height="match_parent"/&gt;
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>tabLayout = (TabLayout) rootView.findViewById(R.id.group_tablayout);
      viewPager = (ViewPager) rootView.findViewById(R.id.group_viewpager);
  
      reference = FirebaseDatabase.getInstance().getReference("groups").child(getArguments().getString("key"));
  
      viewPager.setAdapter(new GroupContentAdapter(getFragmentManager(), reference));
      tabLayout.setupWithViewPager(viewPager);
  </code></pre>
  
  <p>I also realized, that removing by <code>viewPager.setAdapter(new GroupContentAdapter(getFragmentManager(), reference));</code>, the titles won't be modified, so here is the the code for the Adapter</p>
  
  <p>GroupContentAdapter.java</p>
  
  <pre><code>public class GroupContentAdapter extends FragmentPagerAdapter {
  
  public static int SIZE = 3;
  
  private GroupContentFragment[] contents;
  private DatabaseReference reference;
  
  
  public class GroupContentAdapter extends FragmentPagerAdapter {
  
  public static int SIZE = 3;
  
  private GroupContentFragment[] contents;
  private DatabaseReference reference;
  
  
  public GroupContentAdapter(FragmentManager manager, DatabaseReference reference) {
      super(manager);
      this.reference = reference;
      contents = new GroupContentFragment[SIZE];
      contents[0] = GroupContentFragment.newInstance(reference.child(Utils.GROUPORDERS), ContentType.ORDERS);
      contents[1] = GroupContentFragment.newInstance(reference.child(Utils.GROUPMEMBERS), ContentType.MEMBERS);
      contents[2] = GroupContentFragment.newInstance(reference.child(Utils.GROUPMEALS), ContentType.MEALS);
  }
  
  @Override
  public int getCount() {
      return SIZE;
  }
  
  @Override
  public Fragment getItem(int position) {
      return contents[position];
  }
  </code></pre>
  
  <p>}</p>