Chapter 4: Applets and Graphics 1 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Chapter 4 Applets and Graphics

Chapter 4: Applets and Graphics 2 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Java Programs Console application –Plain looking terminal window Graphical application –User interface components (buttons, text input) Applets –Graphical applications that run inside a web browser.

Chapter 4: Applets and Graphics 3 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 1 A Console Application

Chapter 4: Applets and Graphics 4 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 2 A Graphical Application

Chapter 4: Applets and Graphics 5 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Applets Web server (Store a code) Web pages Browser (downloaded) Applets are programs that run inside a web browser. Advantage: others can access your program –Multiple platform (java bytecode) Disadvantage: download time, security

Chapter 4: Applets and Graphics 6 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 3 Web Browsers Accessing a Web Server

Chapter 4: Applets and Graphics 7 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e HTML Java is an object-oriented programming language. An animation of Harry, the horrible Hamster

Chapter 4: Applets and Graphics 8 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e A Simple Applet – – Here is my first applet –

Chapter 4: Applets and Graphics 9 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e A Simple Applet appletviewer RectangleApplet.html – public calss RectangleApplet extends Applet –{ public void paint(Graphic g) – { … – }

Chapter 4: Applets and Graphics 10 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e A Simple Applet Applets don’t have a main method. The web browser is responsible for starting up the Java virtual machine. Graphics (Object)

Chapter 4: Applets and Graphics 11 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 4 The Rectangle Applet in the Applet Viewer

Chapter 4: Applets and Graphics 12 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 5 The Rectan- gle Applet in a Java 2– Enabled Browser

Chapter 4: Applets and Graphics 13 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program RectangleApplet.java import java.applet.Applet; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; public class RectangleApplet extends Applet { public void paint(Graphics g) { // recover Graphics2D Graphics2D g2 = (Graphics2D)g; // construct a rectangle and draw it Rectangle cerealBox = new Rectangle(5, 10, 20, 30); g2.draw(cerealBox);

Chapter 4: Applets and Graphics 14 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e // move rectangle 15 units sideways and 25 units down cerealBox.translate(15, 25); // draw moved rectangle g2.draw(cerealBox); }

Chapter 4: Applets and Graphics 15 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Graphical Shapes Ellips Ellipse2D.Double easterEgg = new Ellipse2D.Double(5, 10, 15, 20) Import java.awt.geom.Ellipse; Line2D.Double segment = new Line2D.Double (x1, y1, x2, y2);

Chapter 4: Applets and Graphics 16 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 6 An Ellipse and Its Bounding Box

Chapter 4: Applets and Graphics 17 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Colors RGB Color magenta = new Color(1.0F, 0.0F, 1.0F); P152

Chapter 4: Applets and Graphics 18 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Fonts G2.drawString(“Applet”, 50, 100); final int HUGE_SIZE = 36; String message = “Applet”; Font hugeFont = new Font (“Serif”, Font. Bold, Huge_SIZE); g2.setFont(hugeFont); g2.setColor(Color.pint); g2.drawString(message, 50, 100);

Chapter 4: Applets and Graphics 19 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 7 Basepoint and Baseline

Chapter 4: Applets and Graphics 20 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 8 Common Fonts

Chapter 4: Applets and Graphics 21 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 9 Text Layout

Chapter 4: Applets and Graphics 22 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 10 The Font Applet

Chapter 4: Applets and Graphics 23 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program FontApplet.java import java.applet.Applet; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Font; import java.awt.font.FontRenderContext; import java.awt.font.TextLayout; public class FontApplet extends Applet { public void paint(Graphics g) { Graphics2D g2 = (Graphics2D)g; // select the font into the graphics context final int HUGE_SIZE = 48; Font hugeFont = new Font("Serif", Font.BOLD, HUGE_SIZE); g2.setFont(hugeFont); String message ="Applet";

Chapter 4: Applets and Graphics 24 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e // create a text layout to measure the string FontRenderContext context = g2.getFontRenderContext(); TextLayout layout = new TextLayout(message, hugeFont, context); // measure the message width and height float xMessageWidth = layout.getAdvance(); float yMessageHeight = layout.getAscent() + layout.getDescent(); // center the message in the window float xLeft = 0.5F * (getWidth()- xMessageWidth); float yTop = 0.5F * (getHeight()- yMessageHeight); float yBase = yTop + layout.getAscent(); g2.drawString(message, xLeft, yBase); }

Chapter 4: Applets and Graphics 25 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Simple Drawings Car drawings

Chapter 4: Applets and Graphics 26 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 11 A Graphical Applet That Draws a Sketch of a Car

Chapter 4: Applets and Graphics 27 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program CarDrawer.java import java.applet.Applet; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import java.awt.geom.Ellipse2D; import java.awt.geom.Line2D; import java.awt.geom.Point2D; public class CarDrawer extends Applet { public void paint(Graphics g) { Graphics2D g2 = (Graphics2D)g; Rectangle body = new Rectangle(100, 110, 60, 10); Ellipse2D.Double frontTire = new Ellipse2D.Double(110, 120, 10, 10); Ellipse2D.Double rearTire = new Ellipse2D.Double(140, 120, 10, 10);

Chapter 4: Applets and Graphics 28 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Point2D.Double r1 = new Point2D.Double(110, 110); // the bottom of the front windshield Point2D.Double r2 = new Point2D.Double(120, 100); // the front of the roof Point2D.Double r3 = new Point2D.Double(140, 100); // the rear of the roof Point2D.Double r4 = new Point2D.Double(150, 110); // the bottom of the rear windshield Line2D.Double frontWindshield = new Line2D.Double(r1, r2); Line2D.Double roofTop = new Line2D.Double(r2, r3); Line2D.Double rearWindshield = new Line2D.Double(r3, r4);

Chapter 4: Applets and Graphics 29 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e g2.draw(body); g2.draw(frontTire); g2.draw(rearTire); g2.draw(frontWindshield); g2.draw(roofTop); g2.draw(rearWindshield); g2.drawString("JavaMobile 1.2ti", 100, 150); }

Chapter 4: Applets and Graphics 30 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 12 Using Graph Paper to Find Shape Coordinates

Chapter 4: Applets and Graphics 31 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 13 Diagrams

Chapter 4: Applets and Graphics 32 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 14 Scene

Chapter 4: Applets and Graphics 33 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 15 Manipulated Image

Chapter 4: Applets and Graphics 34 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Reading Text Input JOptionPane calss showInputDialog method Javax.swing package String input = JOPtionPane.shwInputDialog(“Please enter your age:”); int age = Integer.parseInt(input);\

Chapter 4: Applets and Graphics 35 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 16 An Input Dialog

Chapter 4: Applets and Graphics 36 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program ColorSelect.java import java.applet.Applet; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import javax.swing.JOptionPane; public class ColorSelect extends Applet { public void init() { String input; // ask the user for red, green, blue values input = JOptionPane.showInputDialog("red:"); float red = Float.parseFloat(input); input = JOptionPane.showInputDialog("green:"); float green = Float.parseFloat(input); input = JOptionPane.showInputDialog("blue:"); float blue = Float.parseFloat(input); fillColor = new Color(red,green,blue); }

Chapter 4: Applets and Graphics 37 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e public void paint(Graphics g) { final int SQUARE_LENGTH = 100; Graphics2D g2 = (Graphics2D)g; // select color into graphics context g2.setColor(fillColor); // construct and fill a square whose center is // the center of the window Rectangle square = new Rectangle( (getWidth() - SQUARE_LENGTH) / 2, (getHeight() - SQUARE_LENGTH) / 2, SQUARE_LENGTH, SQUARE_LENGTH); g2.fill(square); } private color fillColor; }

Chapter 4: Applets and Graphics 38 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 17 Intersection of a Line and a Circle

Chapter 4: Applets and Graphics 39 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program Intersect.java import java.applet.Applet; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.geom.Ellipse2D; import java.awt.geom.Line2D; import javax.swing.JOptionPane; public class Intersect extends Applet { public void init() { String input = JOptionPane.showInputDialog("x:"); x = Integer.parseInt(input); } public void paint(Graphics g) { Graphics2D g2 = (Graphics2D)g; double r = 100; // the radius of the circle // draw the circle

Chapter 4: Applets and Graphics 40 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Ellipse2D.Double circle = new Ellipse2D.Double(0, 0, 2 * r, 2 * r); g2.draw(circle); // draw the vertical line Line2D.Double line = new Line2D.Double(x, 0, x, 2 * r); g2.draw(line); // compute the intersection points double a = r; double b = r;

Chapter 4: Applets and Graphics 41 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e double root = Math.sqrt(r * r - (x - a) * (x - a)); double y1 = b + root; double y2 = b - root; // draw the intersection points final double SMALL_CIRCLE_RADIUS = 2; Ellipse2D.Double circle1 = new Ellipse2D.Double( x - SMALL_CIRCLE_RADIUS, y1 - SMALL_CIRCLE_RADIUS, 2 * SMALL_CIRCLE_RADIUS, 2 * SMALL_CIRCLE_RADIUS); Ellipse2D.Double circle2 = new Ellipse2D.Double( x - SMALL_CIRCLE_RADIUS, y2 - SMALL_CIRCLE_RADIUS, 2 * SMALL_CIRCLE_RADIUS, 2 * SMALL_CIRCLE_RADIUS);

Chapter 4: Applets and Graphics 42 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e g2.draw(circle1); g2.draw(circle2); // label the intersection points String label1 = "” + y1; String label2 = "” + y2; g2.drawString(label1, (float)x, (float)y1); g2.drawString(label2, (float)x, (float)y2); } private double x; }

Chapter 4: Applets and Graphics 43 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Program Phoenix.java import java.applet.Applet; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; public class Phoenix extends Applet { public void paint(Graphics g) { Graphics2D g2 = (Graphics2D)g; month = 0; units = new UnitConverter(0, 12, 0, 40, getWidth(), getHeight()); final int JAN_TEMP = 11; final int FEB_TEMP = 13; final int MAR_TEMP = 16; final int APR_TEMP = 20; final int MAY_TEMP = 25; final int JUN_TEMP = 31; final int JUL_TEMP = 33; final int AUG_TEMP = 32; final int SEP_TEMP = 29;

Chapter 4: Applets and Graphics 44 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e final int OCT_TEMP = 23; final int NOV_TEMP = 16; final int DEC_TEMP = 12; drawBar(g2, JAN_TEMP); drawBar(g2, FEB_TEMP); drawBar(g2, MAR_TEMP); drawBar(g2, APR_TEMP); drawBar(g2, MAY_TEMP); drawBar(g2, JUN_TEMP); drawBar(g2, JUL_TEMP); drawBar(g2, AUG_TEMP); drawBar(g2, SEP_TEMP); drawBar(g2, OCT_TEMP); drawBar(g2, NOV_TEMP); drawBar(g2, DEC_TEMP); }

Chapter 4: Applets and Graphics 45 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e public void drawBar(Graphics2D g2, int temperature) { // construct rectangle for this month and temperature Rectangle rect = new Rectangle(month, 0, 1, temperature); // convert to pixel coordinates and draw units.convert(rect); g2.draw(rect); month++; } private int month; private UnitConverter units; }

Chapter 4: Applets and Graphics 46 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 18 Plotting Temperature Data

Chapter 4: Applets and Graphics 47 ©2000, John Wiley & Sons, Inc. Horstmann/Java Essentials, 2/e Figure 19 A Tic-Tac-Toe Board