عدم نمایش عنوان در tabStrip در اندروید استدیو

 apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
buildToolsVersion "23.0.0"

defaultConfig {
        applicationId "com.shadow.hadi.bookproject.bookproject"
minSdkVersion 17
targetSdkVersion 23
versionCode 1
versionName "1.0"
}
    buildTypes {
        release {
            minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:23.0.0'
compile 'com.android.support:design:23.2.0'
}

 public class MainActivity extends AppCompatActivity {

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

    public void SetTabOption(){
        ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
        viewPager.setAdapter(new AdapterFragment(getSupportFragmentManager()));
        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
    }
}

 public class AdapterFragment extends FragmentPagerAdapter {

final int PAGE_COUNT = 3;
    private String tabTitles[] = new String[]{"Tab1","Tab2","Tab3"};

    public AdapterFragment(FragmentManager fm) {
        super(fm);
    }

    @Override
public Fragment getItem(int position) {
        return PageFragment.newInstance(position + 1);
    }

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

 public class PageFragment extends Fragment {

    private int mPage;
    public static final String ARG_PAGE = "ARG_PAGE";

    public static PageFragment newInstance(int page){

        Bundle args = new Bundle();
        args.putInt(ARG_PAGE,page);
        PageFragment fragment = new PageFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override
public void onCreate( Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mPage = getArguments().getInt(ARG_PAGE);
    }


    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,  Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_page,container,false);
        return view;
    }
}