Close all Fragments before the activity in onBackPressed button..

ActivityWithFragments.java

    @Override
    public void onBackPressed() {
        List<Fragment> all_frags = getSupportFragmentManager().getFragments();
        if(all_frags != null){
            if (all_frags.size() == 0) {
                super.onBackPressed();
            } else {
                for (Fragment frag : all_frags) {
                    getSupportFragmentManager().beginTransaction().remove(frag).commit();
                }
            }
        }else{
            super.onBackPressed();
        }
    }