Android SlidingMenu lag at first use

I am experiencing some problems with the slidingmenu library from jfeinstein10: https://github.com/jfeinstein10/SlidingMenu

The problem I observe is that at first use, when the menu opens, it lags showing some black space. Then when I close it and reuse it again, everything is smooth, nothing to declare.

I basically have an Activity extending the SlidingFragmentActivity, and 2 fragments. One for the left menu and another one for the main content.

Here is how I implemented it, I'm investigating this but I really don't know what I've missed:

public class CavendishSlidingFragmentActivity extends SlidingFragmentActivity {

private final String TAG = CavendishSlidingFragmentActivity.class.getName();

protected FragmentManager fragmentManager;
protected Fragment mContent;

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);

    fragmentManager = getSupportFragmentManager();

    DisplayMetrics metrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(metrics);
    getSlidingMenu().setBehindOffset((int) (metrics.widthPixels * 0.2));
}

public void onClickMenu(View v)
{

    if (getSlidingMenu().isMenuShowing())
        getSlidingMenu().showContent();
    else
        getSlidingMenu().showMenu();
}

public void onClickMenuItem(View v)
{

    Long position = (Long) v.getTag();
    switch (position.intValue())
    {
        case Utils.CAT_RESTAURANT:
            showFragment(new RestaurantFragment());
            break;
        case Utils.CAT_SLEEP:
            showFragment(new SleepFragment());
            break;
        case Utils.CAT_DISCOVER:
            showFragment(new DiscoverFragment());
            break;
        case Utils.CAT_TRANSPORT:
            showFragment(new TransportFragment());
            break;
    }
}

private void showFragment(Fragment fragment)
{
    if (mContent != fragment)
    {
        mContent = fragment;
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.main_fragment, fragment);
        fragmentTransaction.commit();
    }

    getSlidingMenu().showContent();
}
}

MainActivity.java

public class MainActivity extends CavendishSlidingFragmentActivity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setBehindContentView(R.layout.fragment_menu);
    setContentView(R.layout.fragment_main);

    // set the Above View Fragment
    if (savedInstanceState != null)
        mContent = fragmentManager.getFragment(savedInstanceState, "mContent");
    if (mContent == null)
    {
        mContent = new RestaurantFragment();
    }

    fragmentManager
            .beginTransaction()
            .replace(R.id.main_fragment, mContent)
            .commit();
}

@Override
public void onSaveInstanceState(Bundle outState)
{
    super.onSaveInstanceState(outState);
    fragmentManager.putFragment(outState, "mContent", mContent);
}

}

I can provide further code but I think the issue might be here, since the menu is drawing itself at first use, causing the lag. I believe I have to force the menu to be drawn before showing it.

Looks like there is something wrong with the library when rendering the menu while it's being opened. My design didn't fit the library I guess, well I just passed to the default Android navigation drawer. Bit different in behavior but the design remains unchanged, works fine for me.