Java tutorial
/* * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * -Redistribution of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * -Redistribution 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 Sun Microsystems, Inc. or the names of contributors may * be used to endorse or promote products derived from this software without * specific prior written permission. * * This software is provided "AS IS," without a warranty of any kind. ALL * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. * * You acknowledge that this software is not designed, licensed or intended * for use in the design, construction, operation or maintenance of any * nuclear facility. */ /* * SelectionDemo.java is a 1.4 application that requires one other file: * images/starfield.gif */ import javax.swing.BoxLayout; import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.event.MouseInputAdapter; import java.awt.*; import java.awt.event.MouseEvent; /* * This displays an image. When the user drags within the image, this program * displays a rectangle and a string indicating the bounds of the rectangle. */ public class SelectionDemo { JLabel label; static String starFile = "starfield.gif"; private void buildUI(Container container, ImageIcon image) { container.setLayout(new BoxLayout(container, BoxLayout.PAGE_AXIS)); SelectionArea area = new SelectionArea(image, this); container.add(area); label = new JLabel("Drag within the image."); label.setLabelFor(area); container.add(label); //Align the left edges of the components. area.setAlignmentX(Component.LEFT_ALIGNMENT); label.setAlignmentX(Component.LEFT_ALIGNMENT); //redundant } public void updateLabel(Rectangle rect) { int width = rect.width; int height = rect.height; //Make the coordinates look OK if a dimension is 0. if (width == 0) { width = 1; } if (height == 0) { height = 1; } label.setText("Rectangle goes from (" + rect.x + ", " + rect.y + ") to (" + (rect.x + width - 1) + ", " + (rect.y + height - 1) + ")."); } /** Returns an ImageIcon, or null if the path was invalid. */ protected static ImageIcon createImageIcon(String path) { java.net.URL imgURL = SelectionDemo.class.getResource(path); if (imgURL != null) { return new ImageIcon(imgURL); } else { System.err.println("Couldn't find file: " + path); return null; } } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event-dispatching thread. */ private static void createAndShowGUI() { //Make sure we have nice window decorations. JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window. JFrame frame = new JFrame("SelectionDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Set up the content pane. SelectionDemo controller = new SelectionDemo(); controller.buildUI(frame.getContentPane(), createImageIcon(starFile)); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { //Schedule a job for the event-dispatching thread: //creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } private class SelectionArea extends JLabel { Rectangle currentRect = null; Rectangle rectToDraw = null; Rectangle previousRectDrawn = new Rectangle(); SelectionDemo controller; public SelectionArea(ImageIcon image, SelectionDemo controller) { super(image); //This component displays an image. this.controller = controller; setOpaque(true); setMinimumSize(new Dimension(10, 10)); //don't hog space MyListener myListener = new MyListener(); addMouseListener(myListener); addMouseMotionListener(myListener); } private class MyListener extends MouseInputAdapter { public void mousePressed(MouseEvent e) { int x = e.getX(); int y = e.getY(); currentRect = new Rectangle(x, y, 0, 0); updateDrawableRect(getWidth(), getHeight()); repaint(); } public void mouseDragged(MouseEvent e) { updateSize(e); } public void mouseReleased(MouseEvent e) { updateSize(e); } /* * Update the size of the current rectangle and call repaint. * Because currentRect always has the same origin, translate it if * the width or height is negative. * * For efficiency (though that isn't an issue for this program), * specify the painting region using arguments to the repaint() * call. * */ void updateSize(MouseEvent e) { int x = e.getX(); int y = e.getY(); currentRect.setSize(x - currentRect.x, y - currentRect.y); updateDrawableRect(getWidth(), getHeight()); Rectangle totalRepaint = rectToDraw.union(previousRectDrawn); repaint(totalRepaint.x, totalRepaint.y, totalRepaint.width, totalRepaint.height); } } protected void paintComponent(Graphics g) { super.paintComponent(g); //paints the background and image //If currentRect exists, paint a box on top. if (currentRect != null) { //Draw a rectangle on top of the image. g.setXORMode(Color.white); //Color of line varies //depending on image colors g.drawRect(rectToDraw.x, rectToDraw.y, rectToDraw.width - 1, rectToDraw.height - 1); controller.updateLabel(rectToDraw); } } private void updateDrawableRect(int compWidth, int compHeight) { int x = currentRect.x; int y = currentRect.y; int width = currentRect.width; int height = currentRect.height; //Make the width and height positive, if necessary. if (width < 0) { width = 0 - width; x = x - width + 1; if (x < 0) { width += x; x = 0; } } if (height < 0) { height = 0 - height; y = y - height + 1; if (y < 0) { height += y; y = 0; } } //The rectangle shouldn't extend past the drawing area. if ((x + width) > compWidth) { width = compWidth - x; } if ((y + height) > compHeight) { height = compHeight - y; } //Update rectToDraw after saving old value. if (rectToDraw != null) { previousRectDrawn.setBounds(rectToDraw.x, rectToDraw.y, rectToDraw.width, rectToDraw.height); rectToDraw.setBounds(x, y, width, height); } else { rectToDraw = new Rectangle(x, y, width, height); } } } }