COMP 110: Spring Announcements Quiz Wednesday No Class Friday Assignment 5 Due next Monday Q&A Review Session Monday

COMP 110: Spring Today in COMP 110 Java Graphics Programming Demo

COMP 110: Spring Computer Graphics Computer Graphics is about producing images with a computer This can be useful in a variety of ways User interfaces (dialog boxes, icons, windows) Special effects (movies, games, etc) Image editing (photoshop) Visualizing scientific data

COMP 110: Spring Graphics in Java Java provides some useful classes & functionality for adding graphics to your programs

COMP 110: Spring Your First Graphics Program import javax.swing.JApplet; import java.awt.Graphics; public class HappyFace extends JApplet { public void paint(Graphics canvas) { canvas.drawOval(100, 50, 200, 200); canvas.fillOval(155, 100, 10, 20); canvas.fillOval(230, 100, 10, 20); canvas.drawArc(150, 160, 100, 50, 180, 180); } Where’s the main method?

COMP 110: Spring Applets public class HappyFace extends JApplet Our HappyFace class inherits from the class JApplet This means that our program is an applet instead of a normal application An applet is program that is meant to be run in a web browser We’ll use it as an easy way to get some graphics capability

COMP 110: Spring Applets Applets do not have a main method They can’t be run like a normal application (using the red running man icon in jGRASP We need to use the apple icon to run the applet

COMP 110: Spring Drawing to Screen public void paint(Graphics canvas) { canvas.drawOval(100, 50, 200, 200); canvas.fillOval(155, 100, 10, 20); canvas.fillOval(230, 100, 10, 20); canvas.drawArc(150, 160, 100, 50, 180, 180); } Applets use a method called paint in order to draw to screen This method is called for you automatically when you start the applet

COMP 110: Spring Screen Coordinate System (0,0) x-axis y-axis (100,50) 50 pixels 100 pixels

COMP 110: Spring Drawing Shapes //draw oval at position 100, 50, of width and height 200 canvas.drawOval(100, 50, 200, 200); //draw a “filled-in” oval at position 155, 100 with w=10, h=20 canvas.fillOval(155, 100, 10, 20); //draw a “filled-in” oval at position x=230, y=100 with w=10, h=20 canvas.fillOval(230, 100, 10, 20); //draw an arc, details in API canvas.drawArc(150, 160, 100, 50, 180, 180);

COMP 110: Spring The Graphics Class What is the canvas object? An object of the Graphics class The graphics class knows how to draw things like shapes to the screen

COMP 110: Spring Setting the Color The Graphics class also provides the capability to change the color that shapes are drawn with Example //draw a yellow oval canvas.setColor(Color.YELLOW); canvas.drawOval(100, 50, 200, 200); //now draw a black oval canvas.setColor(Color.BLACK); canvas.drawOval(100, 50, 200, 200);

COMP 110: Spring Drawing Text to the Screen We can display text on the screen using the drawString method drawString(string, xPos, yPos) Example //print at string and position (60, 75) canvas.drawString("This will be printed to the screen", 60, 75);

COMP 110: Spring String Drawing Example import javax.swing.JApplet; import java.awt.Graphics; public class HappyFace extends JApplet { public void paint(Graphics canvas) { canvas.drawOval(100, 50, 200, 200); canvas.fillOval(155, 100, 10, 20); canvas.fillOval(230, 100, 10, 20); canvas.drawArc(150, 160, 100, 50, 180, 180); canvas.drawString("This is a happy face!", 50, 50); }

COMP 110: Spring Drawing Polygons A polygon is a closed figure made up of line segments that do NOT cross

COMP 110: Spring Drawing Polygons You can draw a polygon by giving the locations of the corners There are two functions you can use drawPolygon Draws an unfilled polygon (just the edges) fillPolygon Draw a filled polygon p1 p2 p3 p4 p5

COMP 110: Spring Drawing Polygons Syntax canvas.drawPolygon(X_Array, Y_Array, Num_Points) canvas.fillPolygon(X_Array, Y_Array, Num_Points) Example int[] xHouse = {150, 150, 200, 250, 250}; int[] yHouse = {100, 40, 20, 40, 100}; canvas.drawPolygon(xHouse, yHouse, xHouse.length);

COMP 110: Spring Creating Dialog Boxes Dialog boxes are special windows that can be used to take input from the user or to display output

COMP 110: Spring Dialog Boxes Dialog boxes can be created using the JOptionPane class import javax.swing.JOptionPane; public class JOptionPaneDemo { public static void main(String[] args) { String name = JOptionPane.showInputDialog("Enter your name:"); JOptionPane.showMessageDialog(null, "Hi " + name + "!"); System.exit(0); }

COMP 110: Spring Input Dialogs Input dialogs take input from the user in the form of a string We use the showInputDialog method of the JOptionPane class Example String name = JOptionPane.showInputDialog("Enter your name:")

COMP 110: Spring Output Dialogs Output dialogs are used to display a message to the user We use the showMessageDialog method of the JOptionPane class Example JOptionPane.showMessageDialog(null, "Hi " + name + "!");

COMP 110: Spring Methods of JOptionPane If showInputDialog and showMessage Dialog are called using the class name JOptionPane, what kind of methods must they be? Static, a JOptionPane object is never created String name = JOptionPane.showInputDialog("Enter your name:"); JOptionPane.showMessageDialog(null, "Hi " + name + "!");

COMP 110: Spring Exiting the Program public static void main(String[] args) { String name = JOptionPane.showInputDialog("Enter your name:"); JOptionPane.showMessageDialog(null, "Hi " + name + "!"); System.exit(0); } At the end of the program we called System.exit(0) This is necessary to get the program end when using things like windows/dialog boxes etc.

COMP 110: Spring Confirmation Windows We can also create dialog boxes that provide the user with the options “Yes” and “No” These are called confirmation windows

COMP 110: Spring Confirmation Windows import javax.swing.JOptionPane; public class JOptionPaneDemo2 { public static void main(String[] args) { while(true) { int answer = JOptionPane.showConfirmDialog(null, "End Program?", "Click Yes or No:", JOptionPane.YES_NO_OPTION); if(answer == JOptionPane.YES_OPTION) System.exit(0); else if(answer == JOptionPane.NO_OPTION) System.out.println("One more time"); else System.out.println("Error"); } } }

COMP 110: Spring Creating the Window int answer = JOptionPane.showConfirmDialog(null, "End Program?", "Click Yes or No:", JOptionPane.YES_NO_OPTION);

COMP 110: Spring Checking the Result if(answer == JOptionPane.YES_OPTION) System.exit(0); else if(answer == JOptionPane.NO_OPTION) System.out.println("One more time"); else System.out.println("Error");

COMP 110: Spring Programming Demo Expand the House Fill the house with a color Draw a door Draw a window Add Text

COMP 110: Spring Programming Demo (150, 100) (150, 40) (200, 20) (250, 40) (250, 100) (0,0) x-axis y-axis (175, 100) (175, 60) (200, 60) (200, 100) (220, 60) (220, 80)(240, 80) (240, 60) (150, 120)

COMP 110: Spring Programming Demo Programming

COMP 110: Spring Wednesday Quiz