I'm trying to show up action button at Toolbar while I'm at fragment (using 1 parent activity) like this: https://developer.android.com/training/implementing-navigation/ancestral.html
This up button must work as standard BackPress. But the main trouble that I've got only one activity with fragment manager and I cannot specify parent activity to it. (http://developer.android.com/training/implementing-navigation/ancestral.html#SpecifyParent)
In other, I using standard workflow:
getMainActivity().getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_HOME | ActionBar.DISPLAY_USE_LOGO | ActionBar.DISPLAY_HOME_AS_UP);
ActionBar ab = getMainActivity().getSupportActionBar();
ab.setDisplayHomeAsUpEnabled(true);
but no result, only back arrow