title: Going back to previous fragment not working correctly
body: <p>I am using a navigation drawer and when I select an item, it correctly replaces the previous fragment with the one I have selected, but if I open another one, and then click the back button, it goes to the previous activity instead of the previous fragment, what is wrong that it is doing this?</p>
  
  <pre><code>private void selectItem(int position) {
      Fragment newFragment;
      FragmentTransaction transaction = getFragmentManager().beginTransaction();
      switch (position){
          case 0:
              //Update
              newFragment = new UpdateFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
          case 1:
              //Maps
              newFragment = new TimetableFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
          case 2:
              //Timetables
              newFragment = new TimetableFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
          case 3:
              //Notes
              newFragment = new TimetableFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
          case 4:
              //About
              newFragment = new AboutFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
          case 5:
              //Settings
              newFragment = new SettingsFragment();
              transaction.replace(R.id.content_frame, newFragment);
              transaction.addToBackStack(null);
              transaction.commit();
              listView.setItemChecked(position, true);
              setTitle(navigationDrawerItems[position]);
              break;
      }
      //listView.setItemChecked(position, true);
      //setTitle(navigationDrawerItems[position]);
      drawerLayout.closeDrawer(listView);
  }
  </code></pre>