在黑莓按钮点击时无法移动到下一个屏幕

Question

这是尝试过的代码，当我点击按钮时，下一个屏幕没有显示....请帮我显示错误

  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
}
}

在这个页面我必须创建一个标签栏我应该如何通过使用选项卡bckground中的图像我尝试在谷歌的scearhing但它没有效果。请帮助我