Horizontally scrollable tabs inside a fragment in action

Question

I need to implement horizontally scrollable tabs inside the Fragmentinside of an already created one Activity. But the class Inventorynaturally extends Fragment, and if I try to extend FragmentActivityfrom Inventory, it does not work.

Inside this:

Put something like this:

import android.app.Fragment;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Inventory extends FragmentActivity {

    ViewPager viewPager = null;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.inventory);
        viewPager = (ViewPager) findViewById(R.id.pager);
        FragmentManager fragmentManager = getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));
    }
}



class MyAdapter extends FragmentPagerAdapter {

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

    @Override
    public android.support.v4.app.Fragment getItem(int position) {
        android.support.v4.app.Fragment fragment = null;
        if (position==0){
            fragment = new Fa();
        }
        if (position==1){
            fragment = new Fb();
        }
        if (position==2){
            fragment = new Fc();
        }
        return fragment;
    }

    @Override
    public int getCount() {
        return 0;
    }

}

In addition, I use this tutorial to implement tabs.