MainActivity.java

public class MainActivity extends ActionBarActivity {

    int number = 1;

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

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        if (savedInstanceState == null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
                @Override
                public void onBackStackChanged() {
                    if(getSupportFragmentManager().getBackStackEntryCount() == 0) finish();
                }
            });

            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, PlaceholderFragment.newInstance(1))
                    .addToBackStack(null)
                    .commit();
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_add) {
            addFragment(++number);
            return true;
        } else if (id == android.R.id.home) {
            onBackPressed();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void addFragment(int number) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, PlaceholderFragment.newInstance(number))
                .addToBackStack(null)
                .commit();
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public static final String ARG_NUMBER = "number";
        private int number;

        public static PlaceholderFragment newInstance(int number) {
            Bundle b = new Bundle();
            b.putInt(ARG_NUMBER, number);

            PlaceholderFragment fragment = new PlaceholderFragment();
            fragment.setArguments(b);

            return fragment;
        }

        public PlaceholderFragment() {
        }

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            number = getArguments().getInt(ARG_NUMBER, 0);
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            TextView textView = (TextView) rootView.findViewById(R.id.num_of_fragment);
            textView.setText("Fragment - " + number);
            return rootView;
        }
    }
}