Activity code for backstack operations with fragments

AndroidFragmentBackStack

public class MainActivity extends BaseActivity implements FragmentManager.OnBackStackChangedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
	getSupportFragmentManager().addOnBackStackChangedListener(this);

        if (savedInstanceState == null) {
            // setupSomeListFragment(); // <= content invocation
	}
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == android.R.id.home) {
            getSupportFragmentManager().popBackStack();
            return false;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onBackPressed() {
        if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
            super.onBackPressed();
        } else {
            getSupportFragmentManager().popBackStack();
        }
    }

    @Override
    public void onBackStackChanged() {
        shouldDisplayHomeUp();
    }

    public void shouldDisplayHomeUp() {
        boolean enableHomeUp = getSupportFragmentManager().getBackStackEntryCount() > 0;
        ActionBar bar = getSupportActionBar();
        if (bar != null) {
            bar.setDisplayHomeAsUpEnabled(enableHomeUp);
        }
    }
}