public abstract class BackStackActivity extends AppCompatActivity implements BackStackManagerInterface {

    private BackStackManager backStackManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        backStackManager = onCreateBackStackManager();
    }

    //Default implementation. Override it to add extra functionality
    protected BackStackManager onCreateBackStackManager() {
        return new BackStackManager(new BackStackHelperListener() {
            @Override
            public void closeApp() {
                BackStackActivity.super.onBackPressed();
            }

            @Override
            public void refresh() {
            }

            @Override
            public void currentTab(Fragment tab) {
            }
        }, getSupportFragmentManager());
    }

    @Override
    public BackStackManager getBackStackManager() {
        return backStackManager;
    }

    protected void setBackStackManager(BackStackManager backStackManager) {
        this.backStackManager = backStackManager;
    }

    @Override
    public void onBackPressed() {

        List fragmentList = getSupportFragmentManager().getFragments();

        boolean handled = false;
        for (Fragment f : (List<Fragment>) fragmentList) {
            if (f.isVisible() && f instanceof BasePostsFragment) {
                handled = ((BasePostsFragment) f).onBackPressed();

                if (handled) {
                    break;
                }
            }
        }

        if (!handled) {
//            super.onBackPressed();
            backStackManager.onBackPressed();
        }

    }
}