ButtonScroll.java Source code

Introduction

Here is the source code for ButtonScroll.java

Source

import java.awt.BorderLayout;
import java.awt.Insets;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JViewport;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class ButtonScroll extends JFrame {
    protected JViewport viewport;

    protected JButton upButton;

    protected JButton downButton;

    protected JButton leftButton;

    protected JButton rightButton;

    protected int pgVertical;

    protected int pgHorzontal;

    public ButtonScroll() {
        super("Scrolling Programmatically");
        setSize(400, 400);
        getContentPane().setLayout(new BorderLayout());

        ImageIcon shuttle = new ImageIcon("largeJava2sLogo.GIF");
        pgVertical = shuttle.getIconHeight() / 5;
        pgHorzontal = shuttle.getIconWidth() / 5;
        JLabel lbl = new JLabel(shuttle);

        viewport = new JViewport();
        viewport.setView(lbl);
        viewport.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent e) {
                enableButtons(ButtonScroll.this.viewport.getViewPosition());
            }
        });
        getContentPane().add(viewport, BorderLayout.CENTER);

        JPanel pv = new JPanel(new BorderLayout());
        upButton = createButton("up", 'u');
        ActionListener lst = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                movePanel(0, -1);
            }
        };
        upButton.addActionListener(lst);
        pv.add(upButton, BorderLayout.NORTH);

        downButton = createButton("down", 'd');
        lst = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                movePanel(0, 1);
            }
        };
        downButton.addActionListener(lst);
        pv.add(downButton, BorderLayout.SOUTH);
        getContentPane().add(pv, BorderLayout.EAST);

        JPanel ph = new JPanel(new BorderLayout());
        leftButton = createButton("left", 'l');
        lst = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                movePanel(-1, 0);
            }
        };
        leftButton.addActionListener(lst);
        ph.add(leftButton, BorderLayout.WEST);

        rightButton = createButton("right", 'r');
        lst = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                movePanel(1, 0);
            }
        };
        rightButton.addActionListener(lst);
        ph.add(rightButton, BorderLayout.EAST);
        getContentPane().add(ph, BorderLayout.SOUTH);

        WindowListener wndCloser = new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        };
        addWindowListener(wndCloser);

        setVisible(true);
        movePanel(0, 0);
    }

    protected JButton createButton(String name, char mnemonics) {
        JButton btn = new JButton(name);
        btn.setToolTipText("Move " + name);
        btn.setBorderPainted(false);
        btn.setMargin(new Insets(0, 0, 0, 0));
        btn.setContentAreaFilled(false);
        btn.setMnemonic(mnemonics);
        return btn;
    }

    protected void movePanel(int xmove, int ymove) {
        Point pt = viewport.getViewPosition();
        pt.x += pgHorzontal * xmove;
        pt.y += pgVertical * ymove;

        pt.x = Math.max(0, pt.x);
        pt.x = Math.min(getMaxXExtent(), pt.x);
        pt.y = Math.max(0, pt.y);
        pt.y = Math.min(getMaxYExtent(), pt.y);

        viewport.setViewPosition(pt);
        enableButtons(pt);
    }

    protected void enableButtons(Point pt) {
        if (pt.x == 0)
            enableComponent(leftButton, false);
        else
            enableComponent(leftButton, true);

        if (pt.x >= getMaxXExtent())
            enableComponent(rightButton, false);
        else
            enableComponent(rightButton, true);

        if (pt.y == 0)
            enableComponent(upButton, false);
        else
            enableComponent(upButton, true);

        if (pt.y >= getMaxYExtent())
            enableComponent(downButton, false);
        else
            enableComponent(downButton, true);
    }

    protected void enableComponent(JComponent c, boolean b) {
        if (c.isEnabled() != b)
            c.setEnabled(b);
    }

    protected int getMaxXExtent() {
        return viewport.getView().getWidth() - viewport.getWidth();
    }

    protected int getMaxYExtent() {
        return viewport.getView().getHeight() - viewport.getHeight();
    }

    public static void main(String argv[]) {
        new ButtonScroll();
    }
}