Japplet中的JPanel

Question

I need to have one JPanel opened on start. I have a button on that one to open to another JPanel which contains a button to bring me back. How do i write action listeners for those buttons. I have searched extensively. Do I need a JFrame ? All examples seem to have it.

Answer 1

Regardless of which approach you might take, the basic idea is the same. You need to know where to go based on where you are...

To this end, this simple example uses a simple navigation interface to provide movement control for the panels and a List to maintain the order of the components.

You could just as simply use a queue of some kind, pushing the next panel onto it and popping the last panel of it as you switched views.

This is a quick and simple example of CardLayout

import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class SwitchPanel extends JApplet{

    private String currentView;
    private List<String> viewNames;

    @Override
    public void init() {
        final CardLayout cardLayout = new CardLayout();
        setLayout(cardLayout);

        Navigator navi = new Navigator() {

            @Override
            public void next() {
                int index = viewNames.indexOf(currentView);
                if (index > -1) {
                    index++;
                    if (index < viewNames.size()) {
                        currentView = viewNames.get(index);
                        cardLayout.show(getContentPane(), currentView);
                    }
                }
            }

            @Override
            public void previous() {
                int index = viewNames.indexOf(currentView);
                if (index > -1) {
                    index--;
                    if (index >= 0) {
                        currentView = viewNames.get(index);
                        cardLayout.show(getContentPane(), currentView);
                    }
                }
            }
        };

        MainPane mainPane = new MainPane(navi);
        LastPane lastPane = new LastPane(navi);

        viewNames = new ArrayList<>(2);
        viewNames.add("main");
        viewNames.add("last");

        add(mainPane, "main");
        add(lastPane, "last");
        currentView = "main";

        cardLayout.show(getContentPane(), "main");

    }

    public interface Navigator {

        public void next();
        public void previous();

    }

    public class MainPane extends JPanel {

        private Navigator navigator;

        public MainPane(Navigator navi) {
            this.navigator = navi;
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            JButton btn = new JButton("Next >");

            add(new JLabel("Main"), gbc);
            add(btn, gbc);
            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    navigator.next();
                }
            });
        }

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

    public class LastPane extends JPanel {

        private Navigator navigator;

        public LastPane(Navigator navi) {
            this.navigator = navi;
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            JButton btn = new JButton("< Previous");

            add(new JLabel("Last"), gbc);
            add(btn, gbc);
            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    navigator.previous();
                }
            });
        }

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

}