add panel to frame in inner listener class?

Question

class MemberBook extends Frame {
        MenuBar     mb;
        Menu        menu;
        MenuItem    miReg, miList, miExit;

        MemberBook() {
                super();

                mb      = new MenuBar();
                menu    = new Menu("Menu");
                miReg   = new MenuItem("Register");
                miList  = new MenuItem("List");
                miExit  = new MenuItem("Exit");

                menu.add(miReg);
                menu.add(miList);
                menu.addSeparator();
                menu.add(miExit);

                mb.add(menu);
                setMenuBar(mb);

                MenuHandler handler = new MenuHandler(this);
                miReg.addActionListener(handler);
                miList.addActionListener(handler);
                miExit.addActionListener(handler);

                setSize(300, 500);
                setVisible(true);
        }

        public static void main(String args[]) {
                MemberBook win = new MemberBook();
        }

        class MenuHandler implements ActionListener {
                MemberBook frame;

                // I want to add panel to outer class but I don't know 
                // other way to do it so, get _frame in constructor
                MenuHandler(MemberBook _frame) {
                        frame = _frame;
                }

                // show different panels for each menu
                public void actionPerformed(ActionEvent e) {
                        String command = e.getActionCommand();

                        if (command.equals("Register")) {
                                RegisterPanel panel = new RegisterPanel();
                                frame.add(panel, "Center");
                        }
                        // else if ...
                }
        }

        // predefined panel to show in MemberBook frame 
        class RegisterPanel extends Panel {
        }                   
}

I want to make pre defined member register panel, member list panel (you can see members list and edit members) and show when choose menu but RegisterPanel doesn't show when I choose register menu. I don't know other way to add panel to frame in inner Listener class, so transferred frame to Listener constructor.

Answer 1

So, the basic answer is, use a CardLayout, see How to Use CardLayout for more details.

import java.awt.CardLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

public class MemberBook {

    public static void main(String[] args) {
        new MemberBook();
    }

    private JMenuBar mb;
    private JMenu menu;
    private JMenuItem miReg, miList, miExit;

    public MemberBook() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {

                mb = new JMenuBar();
                menu = new JMenu("Menu");
                miReg = new JMenuItem("Register");
                miList = new JMenuItem("List");
                miExit = new JMenuItem("Exit");

                menu.add(miReg);
                menu.add(miList);
                menu.addSeparator();
                menu.add(miExit);

                mb.add(menu);

                MainPane mainPane = new MainPane();

                MenuHandler handler = new MenuHandler(mainPane);
                miReg.addActionListener(handler);
                miList.addActionListener(handler);
                miExit.addActionListener(handler);

                JFrame frame = new JFrame();
                frame.setJMenuBar(mb);
                frame.add(mainPane);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public interface MemberBookController {
        public void registerUser();
    }

    public class MainPane extends JPanel implements MemberBookController {

        private CardLayout cardLayout;

        public MainPane() {
            cardLayout = new CardLayout();
            setLayout(cardLayout);

            add(new WelcomePane(), "welcome");
            add(new RegisterPanel(), "register");

            cardLayout.show(this, "welcome");
        }

        @Override
        public void registerUser() {
            cardLayout.show(this, "register");
        }

    }

    public class MenuHandler implements ActionListener {

        private MemberBookController controller;

        // I want to add panel to outer class but I don't know 
        // other way to do it so, get _frame in constructor
        MenuHandler(MemberBookController controller) {
            this.controller = controller;
        }

        // show different panels for each menu
        public void actionPerformed(ActionEvent e) {
            String command = e.getActionCommand();

            if (command.equals("Register")) {
                controller.registerUser();
            }
            // else if ...
        }
    }

    public class WelcomePane extends JPanel {

        public WelcomePane() {
            setBorder(new EmptyBorder(16, 16, 16, 16));
            setLayout(new GridBagLayout());
            add(new JLabel("Welcome"));
            setBackground(Color.BLUE);
        }

    }

    // predefined panel to show in MemberBook frame 
    public class RegisterPanel extends JPanel {

        public RegisterPanel() {
            setBorder(new EmptyBorder(16, 16, 16, 16));
            setLayout(new GridBagLayout());
            add(new JLabel("Register"));
            setBackground(Color.RED);
        }

    }
}

This example also demonstrates the use of a interface to provide "information hiding". The MenuHandler doesn't really need access to the frame or base pane, in fact, it shouldn't care. All it needs to do is tell interested parties that some action has occurred.

I might consider using the Action API to do this, so you can isolate the functionality a little more, see How to Use Actions for more details.