卡布局显示错误的面板

Question

One panel is added through method where card layout is. And another is passed to a method through the object. The problem is that the Panel of a card Layout is showing panel "1" instead of panel "2",like panel "2" is not even passing to a method. There are no errors....

I tried to simplify code as much as i could:

First class:

     public class Game  extends JFrame {
          private CardLayout cl;
          private JPanel MAIN;
          private JPanel FIRST;

          public Game(){

          FIRST = new JPanel();
          FIRST.setLayout(new BorderLayout());

          cl = new CardLayout();
          MAIN = new JPanel();

          MAIN.setLayout(cl);   

      }
          public void Show(){

            MAIN.add(FIRST, "1");
            cl.show(MAIN, "2");
            add(MAIN);  
      }


          public void addPanel2(JPanel panel){
            MAIN.add(panel, "2");   
      }
}

Second class:

public class meni {
   private JPanel SECOND;
   Game nova = new Game();

   public meni(){

      SECOND = new JPanel();
      SECOND.setLayout(new GridBagLayout());

      nova.addPanel2(SECOND);
   }
}

Main class:

  public static void main(String[] args){

      Game ticFrame = new Game();
      meni luk = new meni();

      ticFrame.show();

      ticFrame.setTitle("Hey");
      ticFrame.setSize(600,600);
      ticFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      ticFrame.setLocationRelativeTo(null);
      ticFrame.setVisible(true);
   }
 }

Answer 1

You're adding your second JPanel just fine, but you're adding it to the wrong Game object. A Game object is currently visible on program start up, and within that second class you create a completely new and unique Game object and add your second JPanel to that, so it makes sense that it won't show in the visualized object.

Solution: Don't create a new Game object in the second class, but instead make sure that the second class has a valid reference to the visualized Game object. This can be done through a constructor parameter or a setter method parameter.

Answer 2

nova.addPanel2(SECOND); what do you mean from this code?? to add panel to frame we have methos such as JPanel.add( your panel object).