public class MainActivity extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));


}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position)
        {
            case 0 : Summary summary = new Summary(); return summary ;
            case 1 : Expense_items expenseItems = new Expense_items(); return expenseItems;
            case 2 : Linage_items linage_items= new Linage_items(); return linage_items;
            default: return null;
        }
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }
}
}

public class Summary extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_summary, container, false);
    TextView summary_text = (TextView) rootView.findViewById(R.id.summary_text);
    summary_text.setText("You are in Summary Fragment Fragment");
    FloatingActionButton myFB  = (FloatingActionButton) rootView.findViewById(R.id.fab);

    return rootView;
}
}

<android.support.design.widget.FloatingActionButton
    android:id="@+id/Main_FAB"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="end|bottom"
    android:layout_margin="@dimen/fab_margin"
    app:srcCompat="@android:drawable/ic_dialog_email" />