Java如何在不破坏我的布局的情况下向JFrame添加menuBar

Question

I need some help with adding a menuBar to my JFrame. I have my Gui class:

public class Gui extends JFrame implements KeyListener {
    private PanelMiniMap map;
private CardLayout cardLayout = new CardLayout();

private JPanel cards;

public Gui() {
    this.setSize(1000, 800);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);// center
    this.setResizable(false);

    // bauen();
    this.cards = new JPanel(cardLayout);



    this.addListener();
    this.add(cards);

    this.setVisible(true);

}

public void addListener() {
    this.addKeyListener(this);
}

public void addPanelZuCards(PanelSpielfeld spielfeld, PanelCharakterErschaffung charerschaffung, PanelMiniMap map) {

    this.map = map;

    this.cards.add(charerschaffung, "charerschaffung");
    this.cards.add(spielfeld, "spielfeld");
}

public Dimension getDimension() {
    return new Dimension(this.getWidth(), this.getHeight());
}

/**
 * Neue Charaktererschaffung ausgeben
 * 
 * @param charerschaffung
 *            Das Panel, auf dem die Oberflaeche zur Charaktererschaffung
 *            erstellt wird
 */
public void zeigeCharckterPanel() {
    this.cardLayout.show(cards, "charerschaffung");
}

public void zeigeSpielPanel() {
    this.cardLayout.show(cards, "spielfeld");
    this.requestFocus();

}

@Override
public void keyTyped(KeyEvent e) {
}

@Override
public void keyReleased(KeyEvent e) {
}

@Override
public void keyPressed(KeyEvent e) {
    if (e.getKeyCode() == KeyEvent.VK_LEFT) {
        map.move(-1, 0);
        map.repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
        map.move(1, 0);
        map.repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_UP) {
        map.move(0, -1);
        map.repaint();
    }
    if (e.getKeyCode() == KeyEvent.VK_DOWN) {
        map.move(0, 1);
        map.repaint();

    }
}

}

where I add my 2 JPanels(PanelSpielfeld,PanelCharakterErschaffung)) to my Gui, and it locks like this:

and the other card, wich is the same principle, I show the other card after pressing the "starten!" button:

So, if I add a menuBar to the Jframe:

public Gui() {
        this.setSize(1000, 800);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setLocationRelativeTo(null);// center
        this.setResizable(false);

        // bauen();
        this.cards = new JPanel(cardLayout);

        JMenuBar menuBar;
        JMenu menu;
        JMenuItem menuItem;

        menuBar = new JMenuBar();

        menu = new JMenu("A Menu");
        menuItem = new JMenuItem("testitem");

        menu.add(menuItem);
        menuItem = new JMenuItem("3214dx");
        menu.add(menuItem);
        menuItem = new JMenuItem("dwq213m");
        menu.add(menuItem);
        menuBar.add(menu);
        this.add(menuBar);

        this.addListener();     
        this.add(cards);

        this.setVisible(true);
        this.addWindowFocusListener(this);
    }

Nothing is happening, and I don't really understand why. What am I doing wrong or what should I do, to have the same MenuBar on both "cards"?

Edit: I changed

this.add(menuBar)

to:

this.setJMenuBar(menuBar);

and now it locks like this:

I'm still missing something. Do I have to set a specific LayoutManager for the JFrame?

Answer 1

Okay, I'm sorry for wasting your time (who ever reads this). My 2 JPanles are set to the frames prefered size, so the problem was, that the menuBar tock the space that the 2 panels needed and that was destroying my gui.

If I set the size of the 2 JPanels to frame.height -50 it work's: