Invalid redefinition and implementation

I am currently programming an android app, but I have a problem. I want to use GreenDroid for my project, but when compiling the compiler give me an error: Return type is incompatible with Activity.getActionBar (). In my opinion, the problem is with extension and implementation. Because I saw this:

public class GDActivity extends Activity implements ActionBarActivity

      

        
        
        
      

    

and Activity has a getActionBar () method that returns android.app.ActionBar. But the ActionBarActivity interface has getActionBar () which returns greendroid.widget.ActionBar

Can anyone help me resolve this collision? Thank you in advance.