无法更改Java Swing CardLayout中的卡

Question

I have an class named AddAccounts

class AddAccounts extends JPanel {

    JPanel panelCont; //Panel deck
    CardLayout cl;

    public AddAccounts() {

             panelCont=new JPanel();
             cl = new CardLayout();
             panelCont.setLayout(cl);//set Panel Layout to CardLayout
            setPreferredSize(new Dimension(1013, 513));//Set Default Size

    /* Add Panels to the main window or integrate the panels*/
            panelCont.add(new Panel1(), "1");
            panelCont.add(new Panel2(),"2");
            panelCont.add(new Panel3(),"3");
            cl.show(panelCont, "1");
            add(panelCont);    
        }

    public void goNext() {
       cl.show(panelCont, "2");
      // cl.nxet(panelCont);
        System.out.println("method called"); //for debugging purpose
         }

    public void showFirstPanel(){
        cl.show(panelCont, "1");
         }  
}

And two external(separate files) class named Panel1 and panel2() . and I wanna change the cards( from panel1 to panel2 ) when the button is being pressed in panel1 that's why i create above listed method called goNext(), but the problem is I'm not able to change the cards. here how i try to call the goNext()method in Panel1

@Override
public void actionPerformed(ActionEvent event) {
    if (event.getSource() == nextBtn) {
        setMainCategory((String)mainCat.getSelectedItem());
    }
}
public void setMainCategory(String mainCategory){
    this.mainCategory=mainCategory;
   new AddAccounts().goNext();
    //System.out.println("From set Method: "+this.mainCategory);
}

Everything works fine, the System.out.println("method called"); //for debugging purpose get executed and printed on console window but the panels(card)are not changed. please help.. how to make it work.

@haraldK what you said is absolutely correct. but it doesn't help me, concept i trying to implement is I have an JFrame named mainPanel and in mainPanel i have a JSplitPanel JSplitPane rootPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, userPanel, mainContentPane); mainContentPane consists

JTabbedPane mainContentPane = new JTabbedPane(); mainContentPane.setPreferredSize(new Dimension(900, 550)); mainContentPane.setTabPlacement(JTabbedPane.TOP); mainContentPane.addTab("Your Database", new UserRecords()); mainContentPane.addTab("Add Accounts", new AddAccounts());//here is the AddAccounts JPanel mainContentPane.addTab("Update Existing Data", new EditRecords()); mainContentPane.setSelectedIndex(1);

i place buttons on Panel1,Panel2 rather than placing buttons on parent Frame AddAccounts. Here the method goNext is belong to AddAccounts and i want to access it to change the panel(from 1 to 2) when the button is pressed in Panel1. i cannot call the goNext() method directly,since it is the method of AddAccounts class not Panel1. and new AddAccounts().goNext(); doesn't help Directory Structure: mypackage -UserPanel(MainPanelFrame,userPanelJPanel, mainContentPaneTabbedPane) -AddAccounts (goNext()) -Panel1 (nextBtn) -Panel2 (nextBtn)

Answer 1

The problem is not the CardLayout code, rather it is in the setMainCategory method:

new AddAccounts().goNext();

Here you create a new instance of the AddAccounts every time the method is invoked. The panel is flipped on this instance (that is why you see the debug output), but the component is never added to a parent (like a JFrame or JPanel ) and thus never shown. After the method exits, the resulting component is just thrown away.

Instead, you need to add one single AddAccounts to a parent component, and in the setMainCategory method, you just invoke goNext() on this instance.

Here's a fully functional program that demonstrates everything I tried to explain above:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;

public class CardLayoutTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame("CardLayoutTest");
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

                frame.getContentPane().add(new AddAccounts()); // Create single instance here
                frame.pack();
                frame.setLocationRelativeTo(null);

                frame.setVisible(true);
            }
        });
    }

    static class AddAccounts extends JPanel {

        JPanel panelCont; //Panel deck
        CardLayout cl;

        public AddAccounts() {
            panelCont = new JPanel();
            cl = new CardLayout();
            panelCont.setLayout(cl);//set Panel Layout to CardLayout

            /* Add Panels to the main window or integrate the panels*/
            panelCont.add(new ColorPanel(Color.ORANGE), "1");
            panelCont.add(new ColorPanel(Color.GRAY), "2");
            panelCont.add(new ColorPanel(Color.DARK_GRAY), "3");

            cl.show(panelCont, "1");

            add(panelCont);

            add(new JButton(new AbstractAction("First") {
                @Override
                public void actionPerformed(ActionEvent e) {
                    showFirstPanel();
                }
            }));
            add(new JButton(new AbstractAction("Next") {
                @Override
                public void actionPerformed(ActionEvent e) {
                    // This method is similar to your setMainCategory
                    goNext();
                }
            }));
        }

        public void goNext() {
//            cl.show(panelCont, "2");
            cl.next(panelCont); // Allows iterating through all panels
            System.out.println("method called"); //for debugging purpose
        }

        public void showFirstPanel() {
            cl.show(panelCont, "1");
        }

        /// Dummy class to show that page flipping works
        private class ColorPanel extends JPanel {
            public ColorPanel(Color background) {
                setOpaque(true);
                setBackground(background);
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(300, 200);
            }
        }
    }
}

Answer 2

Just tried to create a functional example. Hope this will help you.

import java.awt.CardLayout;

/**
 *
 * @author user
 */
public class MyFrame extends javax.swing.JFrame {

    /**
     * Creates new form MyFrame
     */
    public MyFrame() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        deck = new javax.swing.JPanel();
        firstCard = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        secondCard = new javax.swing.JPanel();
        jLabel2 = new javax.swing.JLabel();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        deck.setLayout(new java.awt.CardLayout());

        firstCard.setLayout(new java.awt.BorderLayout());

        jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        jLabel1.setText("First");
        firstCard.add(jLabel1, java.awt.BorderLayout.CENTER);

        deck.add(firstCard, "card2");

        secondCard.setLayout(new java.awt.BorderLayout());

        jLabel2.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        jLabel2.setText("Second");
        secondCard.add(jLabel2, java.awt.BorderLayout.CENTER);

        deck.add(secondCard, "card3");

        getContentPane().add(deck, java.awt.BorderLayout.CENTER);

        jButton1.setLabel("Go Next");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
        getContentPane().add(jButton1, java.awt.BorderLayout.PAGE_START);

        pack();
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        ((CardLayout)deck.getLayout()).next(deck);
    }                                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MyFrame().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JPanel deck;
    private javax.swing.JPanel firstCard;
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel secondCard;
    // End of variables declaration                   
}