private void changeFragment(int nav) {
        switch (nav) {
            case R.id.nav_twices:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new TwiceFragment()).commit();
                break;
            case R.id.nav_projects:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProjectsFragment()).commit();
                break;
            case R.id.nav_program:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProgramFragment()).commit();
                break;
        }
    }