not able to move to next screen on button click in blackberry

Question

Here is tried code ,when i click button next screen is not appearing....please help me it is showing error

  ButtonField addButton = new ButtonField("sign in ",FIELD_HCENTER){
    protected boolean navigationClick(int status, int time) {
        // TODO Auto-generated method stub
        Secondscreen src = new Secondscreen();
        //Screen SecondScreen;
        UiApplication.getUiApplication().pushScreen(src);

        return super.navigationClick(status, time);
    }
  };
MainLayout.add(hfm);
MainLayout.add(addButton);
add(MainLayout);
}

SecondScreen

package mypackage;
import net.rim.device.api.ui.container.MainScreen;
public  class Secondscreen extends MainScreen  {
// TODO Auto-generated method stub
public Secondscreen()
{
    setTitle(" Second Screen");
    HorizontalFieldManager hfm=new HorizontalFieldManager(Field.USE_ALL_WIDTH);

    hfm.add(new Button("item1"));
    hfm.add(new Button("item2"));
    hfm.add(new Button("item3"));
    setTitle(hfm); //display at top
}
}

in this page i have to create a tab bar how should i do it by using image in tab bckground i tried scearhing in google but it was not effective.please help me