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  2. How to effectively use cardlayout in java in order to switch from panel using buttons inside various panel constructors

How to effectively use cardlayout in java in order to switch from panel using buttons inside various panel constructors

由 ℡╲_俬逩灬. 提交于 2019-11-27 09:10:34

The short answer is don't. The reasons for this is you'll end having to expose the parent container and CardLayout to ALL your sub components, which not only exposes portions of your application to potential mistreatment, it tightly couples the navigation making it difficult to add/remove steps in the future...

A better solution would be to devise some kind of controller interface, which defines what each view could do (for example showHome, nextView, previousView), you would then pass an implementation of this interface to each view. Each view would then use this interface to request a change as the needed to.

The controller would know things like, the current view, the home view and how to move between certain views (next/previous) as required.

Updated with simple example

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.ContainerAdapter;
import java.awt.event.ContainerEvent;
import java.awt.event.HierarchyEvent;
import java.awt.event.HierarchyListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class AllYouViewBelongToMe {

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

    public AllYouViewBelongToMe() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public interface ViewContoller {

        public void goHome();

        public void nextView();

        public void previousView();

    }

    public static class DefaultViewController implements ViewContoller {

        public static final String HOME = "home";

        private Component currentView = null;
        private List<Component> views;
        private Map<Component, String> mapNames;

        private Container parent;
        private CardLayout cardLayout;

        public DefaultViewController(Container parent, CardLayout cardLayout) {
            this.parent = parent;
            this.cardLayout = cardLayout;
            views = new ArrayList<>(25);
            mapNames = new HashMap<>(25);
        }

        public CardLayout getCardLayout() {
            return cardLayout;
        }

        public Container getParent() {
            return parent;
        }

        public void addView(Component comp, String name) {
            if (!HOME.equals(name)) {
                views.add(comp);
            }
            mapNames.put(comp, name);
            getParent().add(comp, name);
        }

        public void removeView(Component comp, String name) {
            views.remove(comp);
            mapNames.remove(comp);
            getParent().remove(comp);
        }

        @Override
        public void goHome() {
            currentView = null;
            getCardLayout().show(getParent(), HOME);
        }

        @Override
        public void nextView() {
            if (views.size() > 0) {
                String name = null;
                if (currentView == null) {
                    currentView = views.get(0);
                    name = mapNames.get(currentView);
                } else {
                    int index = views.indexOf(currentView);
                    index++;
                    if (index >= views.size()) {
                        index = 0;
                    }
                    currentView = views.get(index);
                    name = mapNames.get(currentView);
                }
                getCardLayout().show(getParent(), name);
            }
        }

        @Override
        public void previousView() {
            if (views.size() > 0) {
                String name = null;
                if (currentView == null) {
                    currentView = views.get(views.size() - 1);
                    name = mapNames.get(currentView);
                } else {
                    int index = views.indexOf(currentView);
                    index--;
                    if (index < 0) {
                        index = views.size() - 1;
                    }
                    currentView = views.get(index);
                    name = mapNames.get(currentView);
                }
                getCardLayout().show(getParent(), name);
            }
        }

    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new BorderLayout());

            CardLayout cardLayout = new CardLayout();
            JPanel view = new JPanel(cardLayout);

            final DefaultViewController controller = new DefaultViewController(view, cardLayout);
            controller.addView(createPane("home"), DefaultViewController.HOME);
            controller.addView(createPane("Page #1"), "View1");
            controller.addView(createPane("Page #2"), "View2");
            controller.addView(createPane("Page #3"), "View3");
            controller.addView(createPane("Page #4"), "View4");

            controller.goHome();

            JPanel controls = new JPanel();
            JButton btnPrev = new JButton("<");
            JButton btnHome = new JButton("Home");
            JButton btnNext = new JButton(">");

            controls.add(btnPrev);
            controls.add(btnHome);
            controls.add(btnNext);

            btnNext.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    controller.nextView();
                }
            });
            btnPrev.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    controller.previousView();
                }
            });
            btnHome.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    controller.goHome();
                }
            });

            add(view);
            add(controls, BorderLayout.SOUTH);

        }

        protected JPanel createPane(String name) {

            JPanel panel = new JPanel(new GridBagLayout());
            panel.add(new JLabel(name));

            return panel;

        }
    }

}
标签
java
swing
button
user-interface
cardlayout
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