Java example source code file (Ruler.java)

This example Java source code file (Ruler.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, background, color, componentadapter, event, f_height, graphics2d, gui, jpopupmenu, keyadapter, mouseadapter, opacity, override, reflection, ruler, runnable, shape, swing

The Ruler.java Java example source code

/*
 * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */

package transparentruler;


import java.awt.*;
import java.awt.GraphicsDevice.WindowTranslucency;
import static java.awt.GraphicsDevice.WindowTranslucency.*;
import java.awt.event.ActionEvent;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Path2D.Float;
import java.lang.reflect.InvocationTargetException;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;


/**
 * This sample demonstrates shaped and translucent window feature.
 * @author Alexander Kouznetsov
 */
@SuppressWarnings("serial")
public class Ruler extends JFrame {

    private static final Color BACKGROUND = Color.RED;
    private static final Color FOREGROUND = Color.WHITE;
    private static final int OPACITY = 180;
    private static final int W = 70;
    private static final int F_HEIGHT = 400;
    private static final int F_WIDTH = (int) (F_HEIGHT * 1.618 + 0.5);

    private static boolean translucencySupported;
    private static boolean transparencySupported;

    private static boolean checkTranslucencyMode(WindowTranslucency arg) {
        GraphicsEnvironment ge =
                GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gd = ge.getDefaultScreenDevice();
        return gd.isWindowTranslucencySupported(arg);
    }

    public Shape buildShape() {
        int h = getHeight();
        int w = getWidth();
        float a = (float) Math.hypot(h, w);
        Float path = new java.awt.geom.Path2D.Float();
        path.moveTo(0, 0);
        path.lineTo(w, 0);
        path.lineTo(0, h);
        path.closePath();
        path.moveTo(W, W);
        path.lineTo(W, h - W * (a + h) / w);
        path.lineTo(w - W * (a + w) / h, W);
        path.closePath();
        return path;
    }

    private final ComponentAdapter componentListener = new ComponentAdapter() {

        /**
         * Applies the shape to window. It is recommended to apply shape in
         * componentResized() method
         */
        @Override
        public void componentResized(ComponentEvent e) {

            // We do apply shape only if PERPIXEL_TRANSPARENT is supported
            if (transparencySupported) {
                setShape(buildShape());
            }
        }
    };

    private final Action exitAction = new AbstractAction("Exit") {

        {
            putValue(Action.MNEMONIC_KEY, KeyEvent.VK_X);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            System.exit(0);
        }
    };

    private final JPopupMenu jPopupMenu = new JPopupMenu();

    {
        jPopupMenu.add(new JMenuItem(exitAction));

        // To avoid popup cutting by main window shape forbid light-weight popups
        jPopupMenu.setLightWeightPopupEnabled(false);
    }

    /**
     * Implements mouse-related behavior: window dragging and popup menu
     * invocation
     */
    private final MouseAdapter mouseListener = new MouseAdapter() {

        int x, y;

        @Override
        public void mousePressed(MouseEvent e) {
            if (e.getButton() == MouseEvent.BUTTON1) {
                x = e.getX();
                y = e.getY();
            }
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if ((e.getModifiersEx() & MouseEvent.BUTTON1_DOWN_MASK) != 0) {
                setLocation(e.getXOnScreen() - x, e.getYOnScreen() - y);
            }
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            if (e.isPopupTrigger()) {
                jPopupMenu.show(getContentPane(), e.getX(), e.getY());
            }
        }
    };

    /**
     * Implements keyboard navigation. Arrows move by 5 pixels, Ctrl + arrows
     * move by 50 pixels, Alt + arrows move by 1 pixel.
     * Esc exits the application.
     */
    private final KeyAdapter keyboardListener = new KeyAdapter() {

        @Override
        public void keyPressed(KeyEvent e) {
            int step = e.isControlDown() ? 50 : e.isAltDown() ? 1 : 5;
            switch (e.getKeyCode()) {
                case KeyEvent.VK_LEFT:
                    setLocation(getX() - step, getY());
                    break;
                case KeyEvent.VK_RIGHT:
                    setLocation(getX() + step, getY());
                    break;
                case KeyEvent.VK_UP:
                    setLocation(getX(), getY() - step);
                    break;
                case KeyEvent.VK_DOWN:
                    setLocation(getX(), getY() + step);
                    break;
                case KeyEvent.VK_ESCAPE:
                    exitAction.actionPerformed(null);
            }
        }
    };

    public Ruler() {
        setUndecorated(true);

        // Enables perpixel translucency
        setBackground(new Color(BACKGROUND.getRed(), BACKGROUND.getGreen(),
                BACKGROUND.getBlue(), OPACITY));

        addMouseListener(mouseListener);
        addMouseMotionListener(mouseListener);
        addComponentListener(componentListener);
        addKeyListener(keyboardListener);
        setContentPane(new JPanel() {

            @Override
            protected void paintComponent(Graphics g) {
                Graphics2D gg = (Graphics2D) g.create();
                int w = getWidth();
                int h = getHeight();
                int hh = gg.getFontMetrics().getAscent();

                // This is an approach to apply shape when PERPIXEL_TRANSPARENT
                // isn't supported
                if (!transparencySupported) {
                    gg.setBackground(new Color(0, 0, 0, 0));
                    gg.clearRect(0, 0, w, h);
                    gg.clip(buildShape());

                    gg.setBackground(Ruler.this.getBackground());
                    gg.clearRect(0, 0, w, h);
                }

                gg.setColor(FOREGROUND);
                for (int x = 0; x < w * (h - 8) / h - 5; x += 5) {
                    boolean hi = x % 50 == 0;
                    gg.drawLine(x + 5, 0, x + 5,
                            hi ? 20 : (x % 25 == 0 ? 13 : 8));
                    if (hi) {
                        String number = Integer.toString(x);
                        int ww = gg.getFontMetrics().stringWidth(number);
                        gg.drawString(number, x + 5 - ww / 2, 20 + hh);
                    }
                }

                gg.dispose();
            }
        });
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(F_WIDTH, F_HEIGHT);
        setLocationByPlatform(true);
    }

    /**
     * @param args the command line arguments are ignored
     */
    public static void main(String[] args) throws InterruptedException, InvocationTargetException {

        SwingUtilities.invokeAndWait(new Runnable() {

            @Override
            public void run() {
                translucencySupported = checkTranslucencyMode(PERPIXEL_TRANSLUCENT);
                transparencySupported = checkTranslucencyMode(PERPIXEL_TRANSPARENT);

                if (!translucencySupported) {
                    System.err.println("This application requires "
                            + "'PERPIXEL_TRANSLUCENT' translucency mode to "
                            + "be supported.");
                    System.exit(-1);
                }

                Ruler ruler = new Ruler();
                ruler.setVisible(true);
            }
        });
    }
}