TabLayout don't get populated with ViewPager at all

Question

I try to populate a TabLayout with a ViewPager but unfortunately it doesn't get populated.

I followed this tutorial to get in touch: TabLayout and ViewPager in your Android App. The tutorial uses the old Support Library v4. My project is based on AndroidX and i want to stay with it. The official documentation of TabLayout said that I need to create the TabLayout inside the ViewPager but that's not working at all. So i created the following XML layout file:

<LinearLayout
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">


    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <com.google.android.material.tabs.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/primaryColor"
            app:tabGravity="fill"
            app:tabMode="fixed"
            app:tabTextColor="@color/primaryTextColor" />

    </androidx.viewpager.widget.ViewPager>

</LinearLayout>

I setup the ViewPager with the following lines to connect TabLayout with ViewPager:

public class MyActivity extends AppCompatActivity {
    ...
    @Override
    public void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_layout);
        ...
        // tab layout
        ViewPager viewPager = findViewById(R.id.viewpager);
        MyFragmentPagerAdapter adapter = new MyFragmentPagerAdapter(this, getSupportFragmentManager());
        viewPager.setAdapter(adapter);
        TabLayout tabLayout = findViewById(R.id.tab_layout);
        tabLayout.setupWithViewPager(viewPager);
        ...
    }
    ...
}

My Adapter is a FragmentPagerAdapter

public class MyFragmentPagerAdapter extends FragmentPagerAdapter {

    private Context context;

    public MyFragmentPagerAdapter(Context context, FragmentManager fm) {
        super(fm);
        this.context = context;
    }

    @Override
    public Fragment getItem(int position) {
        if (position == 0) {
            return new MyFragment1();
        } else {
            return new MyFragment2();
        }
    }

    @Override
    public int getCount() {
        return 2;
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return context.getString(R.string.building);
            case 1:
                return context.getString(R.string.buff);
            default:
                return null;
        }
    }
}

One of my Fragments looks like this:

public class MyFragment1 extends Fragment {

    public MyFragment () {
        // Required empty public constructor
    }

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

}

Here is a picture how it looks like:

Empty ViewPager

Question

So why is the TabLayout not populated at all? I'm working with Android Studio and the Design Manager just shows me an empty TabLayout and ViewPager. I guess, it would precompile the TabLayout but it is just empty...

Please help me because i stuck at this topic. I really want to code it like this to get benefit of swiping tabs and stuff.

Thanks a lot!

Answer 1

I found a solution on another thread Use Tab layout in MVVM architecture with the data binding library. I'm using Android Data Binding so the TabLayout wasn't assigned to the ViewPager. So my code was correct but not accordingly to the Data Binding.

Nevertheless, thanks for your posts here!